LibGUI: Run TextEditor::on_change callback immediately

This is the only Widget that ran its callback in deferred_invoke(). It
seems to be a holdover from when syntax-highlighting ran whenever the
text changed, but that has not been true since
bec2b3086c195e50f233e01f7ab935ba15ac843e. Running the callback
immediately has no obvious downsides, but does make it a lot easier to
reason about. (I might have spent an hour confused as to why things
were happening in the wrong order...)

Userland/Libraries/LibGUI/TextEditor.cpp

@@ -1576,14 +1576,8 @@ void TextEditor::did_change(AllowCallback allow_callback)
     recompute_all_visual_lines();
     hide_autocomplete_if_needed();
     m_needs_rehighlight = true;
-    if (!m_has_pending_change_notification) {
-        m_has_pending_change_notification = true;
-        deferred_invoke([this, allow_callback] {
-            m_has_pending_change_notification = false;
-            if (on_change && allow_callback == AllowCallback::Yes)
-                on_change();
-        });
-    }
+    if (on_change && allow_callback == AllowCallback::Yes)
+        on_change();
 }
 void TextEditor::set_mode(const Mode mode)
 {

Userland/Libraries/LibGUI/TextEditor.h

@@ -361,7 +361,6 @@ private:
     bool m_ruler_visible { false };
     bool m_gutter_visible { false };
     bool m_needs_rehighlight { false };
-    bool m_has_pending_change_notification { false };
     bool m_automatic_indentation_enabled { false };
     WrappingMode m_wrapping_mode { WrappingMode::NoWrap };
     bool m_visualize_trailing_whitespace { true };