Add database_id section in firebase rule release sample

[pl04351820]

Improve the documentation to explain how to use Firebase Rule with Firestore named database

[github-actions]

Hello! I am a robot. Tests will require approval from a repository maintainer to run.

@zli82016, a repository maintainer, has been assigned to review your changes. If you have not received review feedback within 2 business days, please leave a comment on this PR asking them to take a look.

You can help make sure that review is quick by doing a self-review and by running impacted tests locally.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 2 files changed, 2 insertions(+), 2 deletions(-))
google-beta provider: Diff ( 2 files changed, 2 insertions(+), 2 deletions(-))

[modular-magician]

Tests analytics

Total tests: 4
Passed tests: 3
Skipped tests: 0
Affected tests: 1

Click here to see the affected service packages

• firebaserules

Action taken

Found 1 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit. Click here to see the affected tests

TestAccFirebaserulesRelease_FirestoreReleaseHandWritten

Get to know how VCR tests work

[modular-magician]

$\textcolor{green}{\textsf{Tests passed during RECORDING mode:}}$
TestAccFirebaserulesRelease_FirestoreReleaseHandWritten[Debug log]

$\textcolor{green}{\textsf{No issues found for passed tests after REPLAYING rerun.}}$

---

$\textcolor{green}{\textsf{All tests passed!}}$
View the build log or the debug log for each test

[zli82016]

LGTM