search-engine-tracker: Fix the content search in 'shell overview'

Fix a bug that is not possible to search by content
in the shell overview.

In the Nautilus interface, it is possible to search
both by filenames and by content. But in shell overview not.

This bug was introduced in commit f4942473, but this new commit
doesn't not restores the previous behavior.

Fixes: #1437
2 jobs for patch-3 in 13 minutes and 59 seconds
latest
Status Job ID Name Coverage
  Test
passed #663978
flatpak
flatpak devel

00:13:58

passed #663979
style check

00:02:30