Bump version to 31.0.1 and update changelog (#1101)

Change-Id: I0f665fdb9b598e729dfd0975450486e26e116a9d

Co-authored-by: Aalap Shastri <aalapshastri@google.com>

Author: ajs424

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 31.0.1
+*    Updated protobuf constraint in to be less restrictive for users on the Protobuf 3.x series and preserve backwards compatibility.
+
 ## 31.0.0
 *    Compatibility with v21.0 of the API: https://developers.google.com/google-ads/api/docs/release-notes
 *    Added support for declaring EU political advertising status on campaign creation in examples.

src/Google/Ads/GoogleAds/Constants.php

@@ -27,5 +27,5 @@ class Constants
     public const LIBRARY_NAME = 'gccl';
 
     // The library version.
-    public const LIBRARY_VERSION = '31.0.0';
+    public const LIBRARY_VERSION = '31.0.1';
 }