refactor: remove git:unlock command

This is no longer necessary with improvements elsewhere in Dokku.

tests/unit/git_6.bats

@@ -1,30 +0,0 @@
-#!/usr/bin/env bats
-
-load test_helper
-
-setup() {
-  global_setup
-  touch /home/dokku/.ssh/known_hosts
-  chown dokku:dokku /home/dokku/.ssh/known_hosts
-  mkdir -p "$DOKKU_LIB_ROOT/data/git/$TEST_APP"
-  chown dokku:dokku "$DOKKU_LIB_ROOT/data/git/$TEST_APP"
-}
-
-teardown() {
-  rm -f /home/dokku/.ssh/id_rsa.pub || true
-  global_teardown
-}
-
-@test "(git) git:unlock [success]" {
-  run /bin/bash -c "dokku git:unlock $TEST_APP --force"
-  echo "output: $output"
-  echo "status: $status"
-  assert_success
-}
-
-@test "(git) git:unlock [missing arg]" {
-  run /bin/bash -c "dokku git:unlock"
-  echo "output: $output"
-  echo "status: $status"
-  assert_failure
-}