fix(http): use params without RequestOptions

[cexbrayat]

params has been introduced in 4.0.0-beta.0

Before:

http.get(url, new RequestOptions({params: searchParams}))

After:

http.get(url, {params: searchParams})

Fixes #14100

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/angular/angular/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior? (You can also link to an open issue here)

See #14100

http.get(url, new RequestOptions({params: searchParams}))

What is the new behavior?

http.get(url, {params: searchParams})

Does this PR introduce a breaking change? (check one with "x")

[ ] Yes
[x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

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