refactor(router): add type annotation for UrlSegment.parameterMap

[gagern]

Having the type specified explicitly makes the API reference more readable.

PR Checklist

Please check if your PR fulfills the following 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)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.io application / infrastructure changes
• Other... Please describe:

Please double-check my choice.

What is the current behavior?

Issue Number: N/A

Reading https://angular.io/api/router/UrlSegment, the type of parameterMap is unclear. I had to dig through code to work it out.

What is the new behavior?

The type is fully annotated so documentation can reference it clearly.

Does this PR introduce a breaking change?

• Yes
• No

[gagern]

ci/circleci: legacy-unit-tests-saucelabs currently fails stating “Disconnected , because no message in 300000 ms”. Doesn't sound related to my change. Is that test flaky? https://app.circleci.com/pipelines/github/angular/angular suggests it has been failing on a number of recent runs. @atscott can you trigger a re-run?

[atscott]

@gagern Yes, this test is known to be flaky at the moment. Marking as merge-ready

[ngbot]

I see that you just added the action: merge label, but the following checks are still failing:
     status "ci/circleci: legacy-unit-tests-saucelabs" is failing
     missing required status "cla/google"

If you want your PR to be merged, it has to pass all the CI checks.

If you can't get the PR to a green state due to flakes or broken master, please try rebasing to master and/or restarting the CI job. If that fails and you believe that the issue is not due to your change, please contact the caretaker and ask for help.

[atscott]

merge-assistance: Unrelated test failure

[AndrewKushnir]

This PR was merged into the repository by commit aac579d.

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