Reset Shader Editor scroll when changing shader

(cherry picked from commit 0ac5be1e673836390c142ce16bccf49d04d337a9)

editor/plugins/shader_editor_plugin.cpp

@@ -55,6 +55,8 @@ void ShaderTextEditor::set_edited_shader(const Ref<Shader> &p_shader) {
 
 	get_text_edit()->set_text(p_shader->get_code());
 	get_text_edit()->clear_undo_history();
+	get_text_edit()->call_deferred("set_h_scroll", 0);
+	get_text_edit()->call_deferred("set_v_scroll", 0);
 
 	_validate_script();
 	_line_col_changed();