message: Update code owners for the various search backend plugins.
diff: /plugins/cost-insights @backstage/silver-lining
  /plugins/cloudbuild @trivago/ebarrios
  /plugins/search @backstage/techdocs-core
  -/plugins/search-indexer-backend @backstage/techdocs-core
  +/plugins/search-* @backstage/techdocs-core
  /plugins/techdocs @backstage/techdocs-core
  /plugins/techdocs-backend @backstage/techdocs-core
  /packages/techdocs-common @backstage/techdocs-core
  