docs: add HeroService to code tabs and fix headers

[kapunahelewong]

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
[x] Documentation content changes
[ ] angular.io application / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #22359

What is the new behavior?

Adds HeroService to code tabs in Final Code Review.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[mary-poppins]

You can preview 744279e at https://pr22373-744279e.ngbuilds.io/.
You can preview 60389ea at https://pr22373-60389ea.ngbuilds.io/.

[mary-poppins]

You can preview 69186bc at https://pr22373-69186bc.ngbuilds.io/.

[mary-poppins]

You can preview 1053568 at https://pr22373-1053568.ngbuilds.io/.

[kapunahelewong]

Hey @petebacondarwin could you help me figure out why the page I've edited won't render? https://pr22373-1053568.ngbuilds.io/tutorial/toh-pt5 Maybe some spacing is off?

[jenniferfell]

Master/Detail Components and Routing aren't loading right now. Blank pages. @petebacondarwin do you have any ideas? I've checked routing line-for-line, and I don't recognize anything that would break it. Thanks!

[jenniferfell]

Master/Detail Components and Routing aren't loading. Blank pages.

[gkalpak]

This is a known issue #22493. Will be fixed by #22504 (which is marked for merge). Make sure to rebase on master once that's merged.

[ralshammrei2]

add HeroService to code tabs and fix headers #22373

[mary-poppins]

You can preview 7e0734e at https://pr22373-7e0734e.ngbuilds.io/.

[kapunahelewong]

Hey @jenniferfell want to take a look? Rebased after #22504 was merged.

The failures were unrelated to this PR and have been fixed.

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