Revert "Add missing SNAME macro optimization to all theme methods call"

This reverts commit a988fad9a0.

As discussed in #57725 and clarified in #57788, `SNAME` is not meant to be used
everywhere but only in critical code paths. For theme methods specifically, it
was by design that only getters use `SNAME` and not setters.

editor/editor_spin_slider.cpp

@@ -268,7 +268,7 @@ void EditorSpinSlider::_update_value_input_stylebox() {
 		stylebox->set_default_margin(SIDE_RIGHT, 0);
 	}
 
-	value_input->add_theme_style_override(SNAME("normal"), stylebox);
+	value_input->add_theme_style_override("normal", stylebox);
 }
 
 void EditorSpinSlider::_draw_spin_slider() {