region: Remove placeholder text

Placeholder text was marked as translatable, but this is always replaced so
no need to set or translate it.
11 jobs for <span class="ref-name">region-unused-translation</span> in 22 minutes and 11 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #91912
build

00:02:21

 
  Test
passed #91915
armv8

00:13:39

passed #91914
asan

00:02:19

failed #91916
allowed to fail
ppc64le

00:12:57

passed #91913
test

00:00:54

 
  Manual
manual #91917
allowed to fail manual
flatpak
manual #91920
allowed to fail manual
msan
manual #91918
allowed to fail manual
tsan
manual #91919
allowed to fail manual
ubsan
 
  Review
manual #91921
allowed to fail manual
review
manual #91922
allowed to fail manual
stop_review
 
Name Stage Failure
failed
ppc64le Test
Full log written to /cwd/_build/meson-logs/testlog.txt
FAILED: meson-test
/usr/bin/python3 -u /usr/bin/meson test --no-rebuild --print-errorlogs
ninja: build stopped: subcommand failed.
Uploading artifacts...
./*.log: found 1 matching files
_build/meson-logs/: found 4 matching files
Uploading artifacts to coordinator... ok id=91916 responseStatus=201 Created token=ZcoMsCoq
ERROR: Job failed: exit code 1