fix: update codeowner team in repo metadata (#699)

* fix: exclude CODEOWNERS from synthtool * revert changes in synth.py * fix: update codeowner team in repo metadata

Author: anguillanneuf

.repo-metadata.json

@@ -12,6 +12,6 @@
  "repo": "googleapis/java-pubsublite",
  "repo_short": "java-pubsublite",
  "distribution_name": "com.google.cloud:google-cloud-pubsublite",
- "codeowner_team": "@googleapis/api-pubsub",
+ "codeowner_team": "@googleapis/api-pubsublite",
  "api_id": "pubsublite.googleapis.com"
 }