gimp: fix trashed paths

[gromgit]

The actual paths don't have embedded colons:

% /bin/ls -ld Library/Preferences/*gimp* Library/Saved\ Application\ State/*gimp*
-rw-------@ 1 aho  staff  126 Nov 17 22:46 Library/Preferences/org.gimp.gimp-2.10.plist
drwx------@ 4 aho  staff  128 Nov 17 22:46 Library/Saved Application State/org.gimp.gimp-2.10.savedState

Addresses https://github.com/orgs/Homebrew/discussions/5740#discussioncomment-11283702.

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