Fix Wdocumentation warning. NFC.

Author: RKSimon

clang/include/clang/Sema/Sema.h

@@ -5923,8 +5923,6 @@ class Sema final {
   ///
   /// \param OnlyNamespace If true, only considers namespaces in lookup.
   ///
-  /// \param SuppressDiagnostic If true, suppress diagnostic on error.
-  ///
   /// \returns true if an error occurred, false otherwise.
   bool ActOnCXXNestedNameSpecifier(Scope *S,
                                    NestedNameSpecInfo &IdInfo,