all: release v0.19.0

This commit will be tagged v0.19.0.

Change-Id: I8f68c54f930f68f442512b9a72fb7827e28d1147
Reviewed-on: https://code-review.googlesource.com/c/google-api-go-client/+/52490
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Cody Oss <codyoss@google.com>

CHANGES.md

@@ -1,3 +1,10 @@
+# v0.19.0
+
+- Various updates to autogenerated clients.
+
+_Please note:_ the release version is not indicative of an individual client's
+stability or version.
+
 # v0.18.0
 
 - Add the WithClientCertSource option for mTLS (client TLS certificates), currently only supported for HTTP clients.
@@ -6,6 +13,9 @@
 
 - Make DialPool work with WithGRPCConn plus non-zero pool size [googleapis/google-cloud-go#1780](https://github.com/googleapis/google-cloud-go/issues/1780)
 
+_Please note:_ the release version is not indicative of an individual client's
+stability or version.
+
 # v0.17.0
 
 - Revert sqladmin package name back from sql to sqladmin. (#448)