docs: ensure examples get rxjs ^5.5.0

[wardbell]

URGENT - please merge ASAP as we have very little time to update docs before next NG release.

Added patch label as well; RxJS v.5.5 is backward compat for Ng v4

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)
[x] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] angular.io application / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

All doc samples get there node_modules from one place, .../aio/tools/shared/examples/package.json.

This package.json and its yarn.lock are currently pinned to RxJS <5.5 so we can't show or explain the RxJS features that we should now be recommending to everyone.

In user land, people using the CLI are getting 5.5.x today.

Issue Number: #19510 concerning upgrading Docs for v5 Angular and latest CLI

What is the new behavior?

Installs latest RxJS >= 5.5.0

Although the focus is strictly RxJS, the regenerated yarn.lock updates all other package dependencies currently specified in package.json.

That is unintentional but probably a good thing as we should be consistent.
If something goes wrong with this, we will fix it.

Does this PR introduce a breaking change?

[ ] Yes
[x] No - won't affect AIO. Should not affect samples. If it does, we must fix

[mary-poppins]

You can preview 9a8f049 at https://pr19985-9a8f049.ngbuilds.io/.

[gkalpak]

This updates all dependencies, not just RxJS. If that is intentional, it should be reflected in the commit message.

[wardbell]

@gkalpak Huh? Only for samples. All sample are already governed by .../tools/shared/examples/package.js.

Oh ... I see. You mean it will update versions of other packages in package.json that were implied but not installed because existing yarn.lock pinned them. You are correct. That should be OK and if it isn't, we must fix.

I'll be more explicit in the main comment.

Also updated the commit message accordingly

[mary-poppins]

You can preview fca0ed1 at https://pr19985-fca0ed1.ngbuilds.io/.

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