fix(cloud): synced reviewers should be unique

[snakster]

What this PR does / why we need it:

Before, if the same user did multiple reviews, the synced reviewer list would contain duplicates. This PR changes it so that each reviewer is only included once.

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?

no

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[github-actions]

metric: time/op
CloudReadLines-4: old 912µs ± 1%: new 925µs ± 2%: delta: 1.42%
CloudReadLine-4: old 7.08ms ± 1%: new 7.17ms ± 1%: delta: 1.34%
ListFiles-4: old 51.6µs ± 2%: new 51.5µs ± 1%: delta: 0.00%
Generate-4: old 2.59s ± 2%: new 2.56s ± 2%: delta: -1.30%
GenerateRegex-4: old 1.77s ± 1%: new 1.76s ± 1%: delta: -0.45%
TokensForExpressionComplex-4: old 1.13ms ± 0%: new 1.12ms ± 0%: delta: -0.14%
TokensForExpressionPlainStringNoNewline-4: old 929ns ± 1%: new 927ns ± 0%: delta: -0.21%
TokensForExpressionStringWith100Newlines-4: old 32.0µs ± 1%: new 31.9µs ± 1%: delta: -0.37%
TokensForExpressionObjectWith100KeysWithNumberValues-4: old 1.28ms ± 0%: new 1.28ms ± 0%: delta: 0.00%
TokensForExpression-4: old 1.13ms ± 1%: new 1.13ms ± 0%: delta: 0.00%
PartialEvalComplex-4: old 436µs ± 1%: new 436µs ± 1%: delta: 0.00%
PartialEvalSmallString-4: old 3.63µs ± 0%: new 3.62µs ± 0%: delta: -0.24%
PartialEvalHugeString-4: old 1.83ms ± 0%: new 1.84ms ± 0%: delta: 0.38%
PartialEvalHugeInterpolatedString-4: old 4.83ms ± 1%: new 4.82ms ± 1%: delta: 0.00%
PartialEvalObject-4: old 21.7µs ± 1%: new 21.7µs ± 0%: delta: 0.00%
TmAllTrueLiteralList-4: old 5.59ms ± 2%: new 5.56ms ± 0%: delta: -0.46%
TmAllTrueFuncall-4: old 144µs ± 1%: new 144µs ± 1%: delta: 0.41%
TmAnyTrueLiteralList-4: old 130ms ± 1%: new 130ms ± 0%: delta: 0.00%
TmAnyTrueFuncall-4: old 144µs ± 1%: new 144µs ± 1%: delta: -0.39%
TmTernary-4: old 2.55µs ± 0%: new 2.56µs ± 0%: delta: 0.17%
TmTry-4: old 52.7µs ± 1%: new 52.1µs ± 1%: delta: -1.11%
metric: alloc/op
CloudReadLines-4: old 3.12MB ± 0%: new 3.12MB ± 0%: delta: 0.00%
CloudReadLine-4: old 3.37MB ± 0%: new 3.37MB ± 0%: delta: 0.00%
ListFiles-4: old 22.0kB ± 0%: new 22.0kB ± 0%: delta: 0.00%
Generate-4: old 2.31GB ± 0%: new 2.31GB ± 0%: delta: 0.00%
GenerateRegex-4: old 950MB ± 0%: new 950MB ± 0%: delta: 0.00%
TokensForExpressionComplex-4: old 412kB ± 0%: new 412kB ± 0%: delta: 0.00%
TokensForExpressionPlainStringNoNewline-4: old 592B ± 0%: new 592B ± 0%: delta: 0.00%
TokensForExpressionStringWith100Newlines-4: old 14.0kB ± 0%: new 14.0kB ± 0%: delta: 0.00%
TokensForExpressionObjectWith100KeysWithNumberValues-4: old 402kB ± 0%: new 402kB ± 0%: delta: 0.00%
TokensForExpression-4: old 412kB ± 0%: new 412kB ± 0%: delta: 0.00%
PartialEvalComplex-4: old 353kB ± 0%: new 353kB ± 0%: delta: 0.00%
PartialEvalSmallString-4: old 1.74kB ± 0%: new 1.74kB ± 0%: delta: 0.00%
PartialEvalHugeString-4: old 166kB ± 0%: new 166kB ± 0%: delta: 0.00%
PartialEvalHugeInterpolatedString-4: old 4.38MB ± 0%: new 4.38MB ± 0%: delta: 0.00%
PartialEvalObject-4: old 20.4kB ± 0%: new 20.4kB ± 0%: delta: 0.00%
TmAllTrueLiteralList-4: old 1.74MB ± 0%: new 1.74MB ± 0%: delta: 0.00%
TmAllTrueFuncall-4: old 45.5kB ± 0%: new 45.5kB ± 0%: delta: 0.00%
TmAnyTrueLiteralList-4: old 37.9MB ± 0%: new 37.9MB ± 0%: delta: 0.00%
TmAnyTrueFuncall-4: old 45.6kB ± 0%: new 45.6kB ± 0%: delta: -0.00%
TmTernary-4: old 1.11kB ± 0%: new 1.11kB ± 0%: delta: 0.00%
TmTry-4: old 11.1kB ± 0%: new 11.1kB ± 0%: delta: 0.00%
metric: allocs/op
CloudReadLines-4: old 5.54k ± 0%: new 5.54k ± 0%: delta: 0.00%
CloudReadLine-4: old 60.0k ± 0%: new 60.0k ± 0%: delta: 0.00%
ListFiles-4: old 321 ± 0%: new 321 ± 0%: delta: 0.00%
Generate-4: old 25.9M ± 0%: new 25.9M ± 0%: delta: 0.00%
GenerateRegex-4: old 18.3M ± 0%: new 18.3M ± 0%: delta: 0.00%
TokensForExpressionComplex-4: old 4.93k ± 0%: new 4.93k ± 0%: delta: 0.00%
TokensForExpressionPlainStringNoNewline-4: old 21.0 ± 0%: new 21.0 ± 0%: delta: 0.00%
TokensForExpressionStringWith100Newlines-4: old 328 ± 0%: new 328 ± 0%: delta: 0.00%
TokensForExpressionObjectWith100KeysWithNumberValues-4: old 3.29k ± 0%: new 3.29k ± 0%: delta: 0.00%
TokensForExpression-4: old 4.93k ± 0%: new 4.93k ± 0%: delta: 0.00%
PartialEvalComplex-4: old 2.83k ± 0%: new 2.83k ± 0%: delta: 0.00%
PartialEvalSmallString-4: old 23.0 ± 0%: new 23.0 ± 0%: delta: 0.00%
PartialEvalHugeString-4: old 35.0 ± 0%: new 35.0 ± 0%: delta: 0.00%
PartialEvalHugeInterpolatedString-4: old 23.1k ± 0%: new 23.1k ± 0%: delta: 0.00%
PartialEvalObject-4: old 125 ± 0%: new 125 ± 0%: delta: 0.00%
TmAllTrueLiteralList-4: old 13.6k ± 0%: new 13.6k ± 0%: delta: -0.00%
TmAllTrueFuncall-4: old 460 ± 0%: new 460 ± 0%: delta: 0.00%
TmAnyTrueLiteralList-4: old 252k ± 0%: new 252k ± 0%: delta: 0.00%
TmAnyTrueFuncall-4: old 462 ± 0%: new 462 ± 0%: delta: 0.00%
TmTernary-4: old 26.0 ± 0%: new 26.0 ± 0%: delta: 0.00%
TmTry-4: old 144 ± 0%: new 144 ± 0%: delta: 0.00%