build: remove unused, unmaintained Kivy build method

This code has never been used and contains some insecure uses of shell=True
Building Kivy apps should be done with the buildozer=yes method.  The
buildozer method should probably be moved to a provisioner once that is in
place.

.gitlab-ci.yml

@@ -31,6 +31,8 @@ metadata_v0:
     - git checkout $GITCOMMIT
     - cd fdroiddata
     - ../tests/dump_internal_metadata_format.py
+    - sed -i -e '/kivy\W false/d'
+          metadata/dump_*/*.yaml
     - diff -uw metadata/dump_*
 
 debian_testing: