fix: remove pubsublite from internal reporting (#3243)

The `release_level` for the pubsublite Go client is incorrectly thought to be `GA` by a Drift table because of the presence of `cloud.google.com/go/pubsublite/apiv1`.

This PR proposes that we remove `cloud.google.com/go/pubsub/apiv1` entirely for internal reporting (see b/173748364 for context), until the manual library is released.

The alternative is to add the following to `.repo-metadata-full.json`:

```json
  "cloud.google.com/go/pubsublite": {
    "distribution_name": "",
    "description": "Cloud Pub/Sub Lite",
    "language": "Go",
    "client_library_type": "manual",
    "docs_url": "",
    "release_level": "unspecified"
  },
```

@codyoss @hongalex

internal/gapicgen/generator/config.go

@@ -694,7 +694,9 @@ var microgenGapicConfigs = []*microgenConfig{
 		importPath:            "cloud.google.com/go/pubsublite/apiv1",
 		gRPCServiceConfigPath: "google/cloud/pubsublite/v1/pubsublite_grpc_service_config.json",
 		apiServiceConfigPath:  "google/cloud/pubsublite/v1/gapic.yaml",
-		releaseLevel:          "ga",
+		// Update to "ga" after the manual client (beta) for pubsublite is released.
+		// Also make sure the manual client is generated in .repo-metadata-full.json.
+		releaseLevel: "beta",
 	},
 	{
 		inputDirectoryPath:    "google/cloud/automl/v1",