Only add margin to the start of message rows

Allows text to flow right to the edge, important on smaller devices

Also avoids use of child properties which are going away soon
7 jobs for <span class="ref-name">zbrown/message-margin</span> in 11 minutes and 23 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Check
passed #262829
check

00:04:51

 
  Test
failed #262900
flatpak

00:06:32

passed #262899
flatpak

00:28:51

canceled #262898
flatpak

00:00:50

failed #262830
flatpak

00:23:34

 
  Review
skipped #262831
review
skipped #262832
allowed to fail manual
stop_review
 
Name Stage Failure
failed
flatpak Test
free(): invalid next size (fast)
error: Could not compile `semver-parser`.
warning: build failed, waiting for other jobs to finish...
error: build failed
[2/4] Generating org.gnome.FractalDevel.appdata.xml_fractal-gtk@res_merge with a custom command.
FAILED: fractal
/builds/GNOME/fractal/scripts/cargo.sh .. fractal /app/share/locale org.gnome.FractalDevel ' (Development)' 4.0.0-cd750de Devel
ninja: build stopped: subcommand failed.
ERROR: Job failed: exit code 1