Use C-u s SWITCHES <RET> as documented in Updating the Dired Buffer section of the info manual, take only -l as the swithes, which default to -al.

1. Set it per buffer: Use C-u s SWITCHES <RET> as documented in Updating the Dired Buffer section of the info manual, take only -l as the swithes, which defaults to -al.

2. (setq dired-listing-switches "-l") sets it permanently.