As described in the QMenuBar documentation,
a single ampersand in a menu item text is used to
set the shortcut for the menu, while "&&" is used to
get a real ampersand character.

Change-Id: Idf510641c8919ff8223114413851cb3ee7d7b4a2
Reviewed-on: https://gerrit.libreoffice.org/62405
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>