Skip updating the driver tree from Git for the docker image job

We don't use anything from the tree there.
12 jobs for <span class="ref-name">gitlab-ci-GIT_STRATEGY-none</span> in 2 minutes and 2 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Docker Image
passed #62367
debian-testing

00:00:24

 
  Build
passed #62370
xserver-1.13

00:00:30

passed #62371
xserver-1.14

00:00:30

passed #62372
xserver-1.15

00:00:28

passed #62373
xserver-1.16

00:00:30

passed #62374
xserver-1.17

00:00:30

passed #62375
xserver-1.18

00:00:29

passed #62376
xserver-1.18-clang

00:00:32

passed #62377
xserver-1.19

00:00:29

passed #62378
xserver-1.19-clang

00:00:31

passed #62368
xserver-1.20

00:00:41

passed #62369
xserver-1.20-clang

00:00:35