Correct a few remaining metadata entries

[roaks3]

• The PolicyBinding resources were added recently, and share a single resource type
• ApiProxy was a guess for the resource type, but it should actually be Proxy

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