[Clang][Docs] Fix issue number

Fix typo introduced by 6e36ceb

Author: cor3ntin

clang/docs/ReleaseNotes.rst

@@ -292,7 +292,7 @@ Bug Fixes to C++ Support
 - Clang now properly diagnoses missing 'default' template arguments on a variety
   of templates. Previously we were diagnosing on any non-function template
   instead of only on class, alias, and variable templates, as last updated by
-  CWG2032. Fixes (#GH#83461)
+  CWG2032. Fixes (#GH83461)
 
 
 Bug Fixes to AST Handling