The Galaxy theme was the only odd duck to use 26 × 26 pixel icons.
We’ve removed it, but the Change Icon dialog was still reporting
this misleading value.

Spotted by Rizal Muttaqin.

Change-Id: I4f82727b93239a32f7eab5473baa3b8705abde29
Reviewed-on: https://gerrit.libreoffice.org/69148
Tested-by: Jenkins
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>