Update dependabot reviewer list

Signed-off-by: Julius Härtl <jus@bitgrid.net>

.github/dependabot.yml

@@ -9,7 +9,6 @@ updates:
     timezone: Europe/Paris
   open-pull-requests-limit: 10
   reviewers:
-  - juliushaertl
   - violoncelloCH
   ignore:
   - dependency-name: twemoji