user-accounts: Fix namespace of CcUserPanel

It wasn't correctly moved from the UM namespace when renamed in ec529e85.
This hasn't caused a problem, it's just a little confusing.
11 jobs for user-accounts-panel-wrong-namespace in 6 minutes and 8 seconds (queued for 3 minutes and 31 seconds)
Status Job ID Name Coverage
  Build
passed #140380
build

00:01:56

 
  Test
passed #140382
asan

00:02:17

passed #140381
test

00:01:54

 
  Manual
manual #140387
allowed to fail manual
armv8
manual #140383
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flatpak
manual #140386
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msan
manual #140388
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ppc64le
manual #140384
allowed to fail manual
tsan
manual #140385
allowed to fail manual
ubsan
 
  Review
manual #140389
allowed to fail manual
review
manual #140390
allowed to fail manual
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