Create 2021.3.3 on rc (#13375)

Due to version_minor not being updated, a bug existed in NVDA 2021.3.2 where it incorrectly identified itself as 2021.3.1.

Description of how this pull request fixes the issue:
Increases version number, update changelog

source/buildVersion.py

@@ -67,7 +67,7 @@ def formatVersionForGUI(year, major, minor):
 name = "NVDA"
 version_year = 2021
 version_major = 3
-version_minor = 1
+version_minor = 3
 version_build = 0  # Should not be set manually. Set in 'sconscript' provided by 'appVeyor.yml'
 version=_formatDevVersionString()
 publisher="unknown"

user_docs/en/changes.t2t

@@ -3,6 +3,11 @@ What's New in NVDA
 
 %!includeconf: ../changes.t2tconf
 
+= 2021.3.3 =
+This release is identical to 2021.3.2.
+A bug existed in NVDA 2021.3.2 where it incorrectly identified itself as 2021.3.1.
+This release correctly identifies itself as 2021.3.3.
+
 
 = 2021.3.2 =
 This is a minor release to fix several security issues raised.