GDScript: Fix constant conversions

modules/gdscript/tests/scripts/analyzer/features/assymetric_assignment_good.gd

@@ -0,0 +1,16 @@
+const const_color: Color = 'red'
+
+func func_color(arg_color: Color = 'blue') -> bool:
+	return arg_color == Color.BLUE
+
+@warning_ignore("assert_always_true")
+func test():
+	assert(const_color == Color.RED)
+
+	assert(func_color() == true)
+	assert(func_color('blue') == true)
+
+	var var_color: Color = 'green'
+	assert(var_color == Color.GREEN)
+
+	print('ok')