chore(main): release 5.1.0 (#968)

* chore(main): release 5.1.0

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* docs: explain that v2 is not enabled yet

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Alexander Fenster <fenster@google.com>

speech/package.json

@@ -15,7 +15,7 @@
     "test": "c8 mocha system-test --timeout 600000"
   },
   "dependencies": {
-    "@google-cloud/speech": "^5.0.3",
+    "@google-cloud/speech": "^5.1.0",
     "@google-cloud/storage": "^6.0.0",
     "chalk": "^5.0.0",
     "fs.promises": "^0.1.2",