add gh issue id

Author: a-tarasyuk

clang/test/SemaCXX/constant-expression-cxx11.cpp

@@ -2565,7 +2565,7 @@ constexpr GH50055::E2 GlobalInitCE = (GH50055::E2)-1;
 // expected-error@-1 {{constexpr variable 'GlobalInitCE' must be initialized by a constant expression}}
 // expected-note@-2 {{integer value -1 is outside the valid range of values [0, 7] for the enumeration type 'E2'}}
 
-namespace GH {
+namespace GH112140 {
 struct S {
   constexpr S(const int &a = ) { } // expected-error {{expected expression}}
 };