fdo#85620 - Changing the label 'Gallery' and having it in the insert menu

Change-Id: I4deaef9a942b82566bc7dcdc65f2a84441045f91
Reviewed-on: https://gerrit.libreoffice.org/12167
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>