Bug 1816073 - Allow device manager height to grow again. r=settings-reviewers,Gijs

Hmm, I don't recall why I changed this min-height by a height, I didn't
write it down in the commit message either :/

This doesn't regress bug 1801607 and fixes the issue, so should be safe.

Differential Revision: https://phabricator.services.mozilla.com/D169647

browser/themes/shared/preferences/dialog.css

@@ -30,7 +30,7 @@ dialog.doScroll::part(content-box) {
 }
 
 tree:not(#rejectsTree) {
-  height: 15em;
+  min-height: 15em;
 }
 
 .actionButtons {