gplugin/gplugin

Remove the gtk3 stuff from POTFILES that was missed previously

20 months ago, Gary Kramlich
36ab28b74138
Remove the gtk3 stuff from POTFILES that was missed previously

Testing Done:
ran `ninja gplugin-pot`

Reviewed at https://reviews.imfreedom.org/r/1779/
[branchname]
master = default
develop = develop
feature = feature/
release = release/
hotfix = hotfix/
support = support/