[cas] Fix CAS diagnostic ID mapping

Accidentally broken by recent merge resolution.

(cherry picked from commit 9cf7934)

Author: benlangmuir

clang/lib/Basic/DiagnosticIDs.cpp

@@ -220,7 +220,7 @@ CATEGORY(ANALYSIS, SEMA)
 CATEGORY(REFACTORING, ANALYSIS)
 CATEGORY(INSTALLAPI, REFACTORING)
 CATEGORY(TRAP, INSTALLAPI)
-CATEGORY(CAS, INSTALLAPI)
+CATEGORY(CAS, TRAP)
 #undef CATEGORY
 
   // Avoid out of bounds reads.