Update compiler-error-c2103.md

note that this is a C-specific error

Author: TylerMSFT

docs/error-messages/compiler-errors-1/compiler-error-c2103.md

@@ -21,3 +21,6 @@ int main(void)
     int* ptr = &x;   // C2103
 }
 ```
+
+> [!NOTE]
+> This error applies to C code.