Rename the dependencies file to have the correct extension

This isn't a JSON file.

contrib/start-server.sh

 #!/bin/sh
 
-deps_file=/var/lib/gitlab-deps/deps.json
+deps_file=/var/lib/gitlab-deps/deps.list
 
 if [ -z "$GITLAB_URL" ]; then
     echo "Gitlab-deps is not configured (GITLAB_URL empty)" >&2

contrib/update.sh

 #!/bin/sh
 
-deps_file=/var/lib/gitlab-deps/deps.json
+deps_file=/var/lib/gitlab-deps/deps.list
 reload=1
 ret=0