add MySQL 8.4 in google_sql_database_instance documentation

[translucens]

Fixes hashicorp/terraform-provider-google#20579

Release Note Template for Downstream PRs (will be copied)

sql: added MySQL 8.4 in `google_sql_database_instance` documentation

[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 ( 3 files changed, 13 insertions(+), 4 deletions(-))
google-beta provider: Diff ( 3 files changed, 13 insertions(+), 4 deletions(-))

[modular-magician]

Tests analytics

Total tests: 104
Passed tests: 88
Skipped tests: 15
Affected tests: 1

Click here to see the affected service packages

• sql

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

• TestAccSqlDatabaseInstance_activationPolicy

Get to know how VCR tests work

[modular-magician]

🟢 Tests passed during RECORDING mode:
TestAccSqlDatabaseInstance_activationPolicy [Debug log]

🟢 No issues found for passed tests after REPLAYING rerun.

---

🟢 All tests passed!

View the build log or the debug log for each test

[zli82016]

/gcbrun

[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 ( 3 files changed, 13 insertions(+), 4 deletions(-))
google-beta provider: Diff ( 3 files changed, 13 insertions(+), 4 deletions(-))

[modular-magician]

Tests analytics

Total tests: 104
Passed tests: 89
Skipped tests: 15
Affected tests: 0

Click here to see the affected service packages

• sql

🟢 All tests passed!

View the build log

[zli82016]

LGTM