Remove call to SetAlpha as the internal method is being removed (UUM-… (#618)

* Remove call to SetAlpha as the internal method is being removed (UUM-113705)

The ContainerWindow.SetAlpha() method is obsolete functionality that's being removed from the Editor.
This is the only call, which is already non-functional, so there's no risk for breaking behavior.

* Changelog update.

---------

Co-authored-by: Tim Keosababian <36088732+timkeo@users.noreply.github.com>

Author: TimAidleyAtUnity

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - [PBLD-242] Fixed a bug where edges were being incorrectly selected when one or both vertices were behind the camera's near plane, causing flipped lines and inconsistent selection behavior.
 - [PBLD-226] Fixed a bug where ProBuilder faces could not selected when obscured by another GameObject
 - [PBLD-164] Fixed a bug with UV autostitching where the position offset would not take into account the face rotation center offset.
+- [PBLD-253] Removes call to internal API that is being removed.
 
 ## [6.0.6] - 2025-07-01
 

Editor/EditorCore/TooltipEditor.cs

@@ -24,7 +24,6 @@ public static TooltipEditor instance()
                 s_Instance.maxSize = Vector2.zero;
                 s_Instance.hideFlags = HideFlags.HideAndDontSave;
                 s_Instance.ShowTooltip();
-                s_Instance.m_Parent.window.SetAlpha(1f);
             }
 
             return s_Instance;