tools/spec: remove an instance of a C-style cast

C casting produces warnings under our preferred clang warnings. We know
what we're doing (more or less), so keep clang quiet

tools/spec.py

@@ -1028,7 +1028,7 @@ def write_trace(dst: TextIO, q: List[Type], reg: Registry):
             }
             #undef FWD
             
-            #define FWD(NAME) if (!strcmp(#NAME,pName)) { return (PFN_vkVoidFunction)NAME; }
+            #define FWD(NAME) if (!strcmp(#NAME,pName)) { return reinterpret_cast<PFN_vkVoidFunction> (NAME); }
             MAP_INSTANCE_COMMANDS(FWD)
             #undef FWD
             std::clog << "Unhooked: " << pName << '\\n';