Doc: Remove duplicate paragraph in 'Menu QML Type' and add missing ')'

On the documentation for the types of QML menus there is a duplicate paragraph that seems to be of an older version as it doesn't mention Qt::AA_DontUseNativeMenuWindows.

Also, on the same page in the "API differences" section, near the end:
"In addition, showing a popup (using for example open() or popup() will, on some platforms..."
The '(' used before the word "using" is never closed, I believe it meant so say "... (using for example open() or popup()) will, on some...".