feat: Update Compute Engine API to revision 20250302

This fixes the name of an internal proto message that could not be used previously, as per external issue b/323357483.

Generator owners: This is technically a breaking change but is being introduced without a new major version as we believe that customers are unlikely to be using the problematic field, and that it's in the best interests of most customers to keep to a minor release (see b/345025532#comment21 internally). We suggest putting a message like the following in the most appropriate place(s) for your language (version history, release notes, etc.):

This is technically a breaking change but is being introduced without a new major version as we believe that customers are unlikely to be using the problematic field, and that it's in the best interests of most customers to keep to a minor release. (We completely acknowledge that this is a breaking change, and we apologize if users are affected by it. Please [raise an issue](INSERT-LINK) with any concerns - we're keen to improve this balance where we can.)