Change width of last measure on page

Have this arrangement of Feliz Navidad in which I inserted a “new page” marker to have the B part on another page: musescore.com/user/64348498/scores/28866656

Now my last measure is stretched out… I can’t get it to unstreched. I tried:
– Format -> Streching
– Finding a mysterious option “Align last system to page margin” (couldn’t find it)
– Searching for property options in the bar
– Trying to insert a “horizontal box” thing

How is this done properly? I would just bring some other bars down… But I would prefer to have this measure just shorter.