Update google_cloudfunctions_function datasource documentation.

[upodroid]

Fixes: hashicorp/terraform-provider-google#6816

Release Note Template for Downstream PRs (will be copied)

cloudfunctions: Updated the `google_cloudfunctions_function` datasource to include new fields available in the API.

[modular-magician]

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[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 7 insertions(+))
Terraform Beta: Diff ( 1 file changed, 7 insertions(+))

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 7 insertions(+))
Terraform Beta: Diff ( 1 file changed, 7 insertions(+))