[mono] Fix warning in class-internals.h (#91314)

It was supposed to be fixed in #90068 but we should've used `guint` for the one-bit bitfield.

src/mono/mono/metadata/class-internals.h

@@ -504,11 +504,11 @@ struct _MonoGenericContainer {
 	int type_argc    : 29; // Per the ECMA spec, this value is capped at 16 bits
 	/* If true, we're a generic method, otherwise a generic type definition. */
 	/* Invariant: parent != NULL => is_method */
-	gint is_method     : 1;
+	guint is_method     : 1;
 	/* If true, this container has no associated class/method and only the image is known. This can happen:
 	   1. For the special anonymous containers kept by MonoImage.
 	   2. When user code creates a generic parameter via SRE, but has not yet set an owner. */
-	gint is_anonymous : 1;
+	guint is_anonymous : 1;
 	/* Our type parameters. If this is a special anonymous container (case 1, above), this field is not valid, use mono_metadata_create_anon_gparam ()  */
 	MonoGenericParamFull *type_params;
 };