Log Message:
xfce4-tumbler: update to 4.18.1

Change log:

4.18.1 (2023-04-17)
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- Fix memory leak in jpeg-thumbnailer
- Fix memory leak in cover-thumbnailer
- Fix previous commit
- cover-thumbnailer: Fix deprecation warning
- build: Let xdt-depends.m4 macros set GLib macros
- Translation Updates:
  English (Canada), Greek, Korean, Portuguese