CI: enable eval-annotations for vermin

It has happened more than once that Python 3.9+ type annotation have
slipped into the code and broken earlier Python versions. Enable the
eval-annotations flag in vermin to catch that.

Reviewed-by: Oliver Smith <ollieparanoid@postmarketos.org>
Link: https://lists.sr.ht/~postmarketos/pmbootstrap-devel/%3C20230625193650.528651-2-luca@z3ntu.xyz%3E

.ci/vermin.sh

@@ -17,6 +17,7 @@ vermin \
 	--backport typing \
 	--lint \
 	--no-parse-comments \
+	--eval-annotations \
 	$(find . -name '*.py' \
 		-a -not -path "./.venv/*" \
 		-a -not -path "./venv/*")