rows: Don't expand beyond 700px

When the rows grow too wide, they become unbalanced and
gives a sensation of wasted space. This commit makes the
task rows not grow beyong 700px (or 1400px on HiDPI
monitors) and keep center-aligned.
1 job for wip/gbsneto/nonexpanding-rows in 4 minutes and 59 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #371
build-todo

00:04:59