Fix #316125: Dock widgets are now focused on visibilty toggle

[sidharth-anand]

Resolves: https://musescore.org/en/node/316125

This patch modifies the reDisplayDockWidget function in musescore.cpp to make sure that when the visibility of docked widgets like the mixer/inspector is toggled, the widget is focused and appears on top in the dock

• I signed CLA
• I made sure the code in the PR follows the coding rules
• I made sure the code compiles on my machine
• I made sure there are no unnecessary changes in the code
• I made sure the title of the PR reflects the core meaning of the issue you are solving
• I made sure the commit message(s) contain a description and answer the question "Why do those changes fix that particular issue?" or "Why are those changes really necessary as improvements?"
• I made sure the commit message title starts with "fix #424242:" if there is a related issue
• I created the test (mtest, vtest, script test) to verify the changes I made

[Jojo-Schmitz]

What's your username on musescore.org?

[sidharth-anand]

85sid