fix(word-cloud): fix randomness of each word's rotation

[ebaratte]

SUMMARY

In random and square mode, the words rotation of a word cloud chart should be assigned randomly, and be different for each word. Before this PR, all words use the same rotation (derived from the first randomly generated number by seedRandom()).
This PR fixes that behaviour, and restores the randomness of each word's rotation.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Before:

--

After:

TESTING INSTRUCTIONS

Create a word cloud chart, and select a square or random rotation. Ensure all words have different rotations.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[stephenLYZ]

LGTM! Nice work!

[codecov]

Codecov Report

Merging #19977 (5784212) into master (f144de4) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

❗ Current head 5784212 differs from pull request most recent head 1ef3386. Consider uploading reports for the commit 1ef3386 to get more accurate results

@@            Coverage Diff             @@
##           master   #19977      +/-   ##
==========================================
- Coverage   66.29%   66.29%   -0.01%     
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  Files        1712     1712              
  Lines       63962    63963       +1     
  Branches     6731     6731              
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  Hits        42404    42404              
- Misses      19847    19848       +1     
  Partials     1711     1711              

Flag	Coverage Δ
javascript	51.28% <0.00%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
...ns/plugin-chart-word-cloud/src/chart/WordCloud.tsx	0.00% <0.00%> (ø)

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