Modify the public documentation to reduce confusion between gcs bucket and log bucket in iam binding examples

[pengq-google]

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).
• 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 Write release notes before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

[modular-magician]

Hello! I am a robot. It looks like you are a: Community Contributor Googler Core Contributor. Tests will run automatically.

@NickElliot, 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:

Breaking Change(s) Detected

The following breaking change(s) were detected within your pull request.

• Field bucket_options.exponential_buckets.num_finite_buckets changed from optional to required on google_logging_metric - reference
• Field bucket_options.linear_buckets.num_finite_buckets changed from optional to required on google_logging_metric - reference

If you believe this detection to be incorrect please raise the concern with your reviewer. If you intend to make this change you will need to wait for a major release window. An override-breaking-change label can be added to allow merging.

Diff report

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

Terraform GA: Diff ( 3 files changed, 13 insertions(+), 13 deletions(-))
Terraform Beta: Diff ( 3 files changed, 13 insertions(+), 13 deletions(-))

[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, 4 insertions(+), 4 deletions(-))
Terraform Beta: Diff ( 1 file changed, 4 insertions(+), 4 deletions(-))

[NickElliot]

LGTM