Fix TestAccDataSourceSqlDatabaseInstances_* failures in VCR

[shuyama1]

TestAccDataSourceSqlDatabaseInstances_* failed due to that #7044 added a field instance_type to google_sql_database_instance which also needs to be added to google_sql_database_instances datasource.

The reason tests passed in datasource PR #6980 is that the tests was ran prior to the merge of instance_type PR and never got ran after.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

[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.

Terraform GA: Diff ( 1 file changed, 1 insertion(+))
Terraform Beta: Diff ( 1 file changed, 1 insertion(+))
TF Validator: Diff ( 2 files changed, 3 insertions(+), 3 deletions(-))

[modular-magician]

Tests analytics

Total tests: 2400
Passed tests 2148
Skipped tests: 251
Failed tests: 1

Action taken

Triggering VCR tests in RECORDING mode for the tests that failed during VCR. Click here to see the failed tests

TestAccContainerCluster_withInvalidGatewayApiConfigChannel

[modular-magician]

Tests passed during RECORDING mode:
TestAccContainerCluster_withInvalidGatewayApiConfigChannel[Debug log]

All tests passed
View the build log or the debug log for each test

[roaks3]

Awesome, thanks for going ahead and fixing this!