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/plugins/skeleton_3d_editor_plugin.cpp

@@ -602,7 +602,7 @@ void Skeleton3DEditor::update_editors() {
 
 void Skeleton3DEditor::create_editors() {
 	set_h_size_flags(SIZE_EXPAND_FILL);
-	add_theme_constant_override(SNAME("separation"), 0);
+	add_theme_constant_override("separation", 0);
 
 	set_focus_mode(FOCUS_ALL);