Unhook the mouse down hook at the end of PropertyGridView.ProcessEnumUpAndDown (#12508)

* Unhook the mouse down hook at the end of PropertyGridView.ProcessEnumUpAndDown

* Removing ? from code line "EditTextBox?.SelectAll();"

Author: LeafShi1

src/System.Windows.Forms/src/System/Windows/Forms/Controls/PropertyGrid/PropertyGridInternal/PropertyGridView.cs

@@ -2475,7 +2475,8 @@ private bool ProcessEnumUpAndDown(GridEntry entry, Keys keyCode, bool closeDropD
             }
 
             CommitValue(entry, valueNew, closeDropDown);
-            EditTextBox?.SelectAll();
+            EditTextBox.HookMouseDown = false;
+            EditTextBox.SelectAll();
             return true;
         }