Finalize SPIRV-Tools v2020.5

CHANGES

diff --git a/CHANGES b/CHANGES
index 487651a..31c6cb3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,6 @@
 Revision history for SPIRV-Tools
 
-v2020.5-dev 2020-09-22
+v2020.5 2020-09-22
  - General
    - Enable building with BUILD_SHARED_LIBS=1 (#3490)
    - Avoid using /MP4 for clang on windows. (#3662)