Update website doc for data_cache_config

[skysarthak]

Fixes hashicorp/terraform-provider-google#22427

Issue summary: Terraform website docs and CloudSQL doc for data_cache_config are not up to date. This is leading to confusion where users incorrectly expect data_cache_config to default to false for all ENTERPRISE_PLUS edition instances.

Mitigation: CloudSQL doc is now fixed to reflect the most up to date behavior. This PR aims to fix the Terraform website doc.

b/387580491

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).
• 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).
• Generated Terraform providers, and ran make test and make lint in the generated providers to ensure it passes unit and linter tests.
• Ran relevant acceptance tests using my own Google Cloud project and credentials (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.

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Diff report

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

google provider: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))
google-beta provider: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))