When updating a cloud-run service, the PollCheckKnativeStatusFunc checks whether the status.observedGeneration field matches the metadata.generation field to assert that an update operation has finished. The value of metadata.generation is read once (from the response to the PUT operation that updates the service) and not refreshed.

However if a new revision is created during the polling-period then the PollCheckKnativeStatusFunc may never see the generation value that it is looking for.

We have observed this when cloud-run services are managed by terraform but also deployed "out-of-band" by other CI pipelines (e.g. deploying a new container from Github Actions).

1. Terraform creates a new revision, observedGeneration is 1, generation is 2 (expected generation is 2)
2. The operation completes and observedGeneration and generation are now 2
3. Another actor creates a new revision, generation is now 3 but observedGeneration is 2
4. The second operation completes observedGeneration and generation are now 3
5. Terraform polls for the latest observedGeneration and sees that 3 != 2 (expected generation) so continues polling until the timeout.

Since the generation value is a number that increases predictably, it should be safe to use a less-than comparison, so that we can end the poll once the expected generation has passed.

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 the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

cloudrun: Fixed race condition when polling for status during an update of a `google_cloud_run_service`

Derived from GoogleCloudPlatform/magic-modules#7520