LibGUI: Always paint the cursor visible when focusing a TextEditor

If the cursor happened to be blinking in the invisible state, it would
take 500ms before we actually see the cursor in a newly focused editor
widget. This patch makes it show up right away.

Libraries/LibGUI/TextEditor.cpp

@@ -1086,6 +1086,7 @@ void TextEditor::set_cursor(const TextPosition& a_position)
 
 void TextEditor::focusin_event(Core::Event&)
 {
+    m_cursor_state = true;
     update_cursor();
     start_timer(500);
 }