release: v0.5.0

This CL will be tagged 0.5.0.

Change-Id: Id26fc4415a6d9ad759422a6748518a4c7cbb821a
Reviewed-on: https://code-review.googlesource.com/c/google-api-go-client/+/41030
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Tyler Bui-Palsulich <tbp@google.com>
Reviewed-by: Jean de Klerk <deklerk@google.com>

CHANGES.md

@@ -1,3 +1,12 @@
+# v0.5.0
+
+- Better support for google.api.HttpBody.
+- Support for google.api.HttpBody in the healthcare API.
+- Various updates to autogenerated clients.
+
+_Please note:_ the release version is not indicative of an individual client's
+stability or version.
+
 # v0.4.0
 
 - Includes a re-pin of opencensus, greatly reducing the transitive