fmt: fix error of generic struct_init using module (fix #12893) (#12935)

vlib/v/fmt/tests/generic_structs_using_mod_keep.vv

@@ -0,0 +1,8 @@
+import v.fmt.tests.obj
+
+struct GenericStruct<A, B> {
+}
+
+fn main() {
+	_ := GenericStruct<obj.Test, obj.Test>{}
+}

vlib/v/fmt/tests/obj/obj.v

@@ -0,0 +1,3 @@
+module obj
+
+pub struct Test {}