Build: fix a rule in the opam file (the remove script is in etc/lutin, not etc/Lutin)

3 jobs for master in 8 minutes and 58 seconds
Status Job ID Name Coverage
  Build
passed #92449
build

00:04:32

 
  Test
passed #92450
allowed to fail
test_opam_test

00:04:02

 
  Release
passed #92451
release

00:00:23