gplugin/gplugin

Update the POTFILES for the gtk->gtk3 rename

2021-09-30, Gary Kramlich
54627f4294b7
Update the POTFILES for the gtk->gtk3 rename

Testing Done:
ran `ninja gplugin-pot`

Reviewed at https://reviews.imfreedom.org/r/967/
REVIEWBOARD_URL = "https://reviews.imfreedom.org/"
REPOSITORY = "gplugin/gplugin"
REPOSITORY_TYPE = "mercurial"
BRANCH = "default"
LAND_DEST_BRANCH = "default"
LAND_PUSH = False