mouse: Adapt the indentation

This adapts the indentation of the children of HdyColumn, which were
deliberately left intact in the previous commit to make it more
readable.
11 jobs for adaptive-mouse in 5 minutes and 14 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #221844
build

00:02:34

 
  Test
passed #221846
asan

00:02:39

passed #221845
test

00:02:31

 
  Manual
manual #221851
allowed to fail manual
armv8
manual #221847
allowed to fail manual
flatpak
manual #221850
allowed to fail manual
msan
manual #221852
allowed to fail manual
ppc64le
manual #221848
allowed to fail manual
tsan
manual #221849
allowed to fail manual
ubsan
 
  Review
manual #221853
allowed to fail manual
review
manual #221854
allowed to fail manual
stop_review