Updated the release notes and the upb version.

Also removed the obsolete PROTOBUF_VERSION variable now that
upb is updated.

CHANGES.txt

@@ -25,9 +25,14 @@ Unreleased Changes (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
   * 6x speedup in ArrayEncoder.writeUInt32NotTag
 
   Python
-  * Added UnknownFieldSet(message) for pure Python. The old
+  * The C extension module for Python has been rewritten to use the upb library.
-    message.UnknownFields() will be deprecated after UnknownFieldSet(message) is
+    This is expected to deliver significant performance wins, especially when
-    added for cpp extension.
+    parsing large payloads.  There are some minor breaking changes, but these
+    should not impact most users.  For more information see:
+    https://developers.google.com/protocol-buffers/docs/news/2022-05-06#python-updates
+  * Due to the breaking changes for Python, the major version number for Python
+    has been incremented.
+  * The binary wheel for macOS now supports Apple silicon.
 
 2022-04-21 version 3.20.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
 

protobuf_deps.bzl

@@ -114,6 +114,6 @@ def protobuf_deps():
         _github_archive(
             name = "upb",
             repo = "https://github.com/protocolbuffers/upb",
-            commit = "0e8772fc20e5a0a2fa1f326c79d494374871ef94",
+            commit = "32f45b5f33d4399f27f1f6db2ad0ccacb5cabaaf",
-            sha256 = "2a7ccd5a8e20c5b2f6efafb305f734c7ad1cc5615706f7a35cd4fbad436d5101",
+            sha256 = "89c43204ca4e9ac0fed18daff3bd060209f963c89de4aa7a5a66d6968973c03b",
         )

protobuf_version.bzl

@@ -1,6 +1,3 @@
 PROTOC_VERSION = '3.20.1'
 PROTOBUF_JAVA_VERSION = '3.20.1'
 PROTOBUF_PYTHON_VERSION = '3.20.1'
-
-# Remove once upb has been updated to use PROTOBUF_PYTHON_VERSION instead.
-PROTOBUF_VERSION = PROTOBUF_PYTHON_VERSION