Fixes quick action argument handling

Closes #19 (closed)

This MR fixes a problem in how quick action commands were split into the action and arguments.

Checklist

• Manually verified passing unit tests for this branch locally by running bin/run_docker_tests.sh
  • Yes, this is a pain, but GitLab doesn't run reasonably within a docker container in a normal CI pipeline
  • See bin/run_docker_tests.sh --help for faster/iterative testing options
• Paste local test output

Local Test Output

/bin/run_docker_tests.sh output

[>>>] Will not kill docker container (can be re-used)
[>>>] Retrieving token
[>>>] GitLab should be ready
[>>>] Pasteable config into bin/.env: 
[>>>] 
export DISCOTO_GITLAB_ENDPOINT=http://172.17.0.2
export DISCOTO_GITLAB_TOKEN=vuBg8vds5dG9vn7uD1hp
export DISCOTO_PROJECTS=test-group/test-project
export DISCOTO_GROUPS=test-group
export DISCOTO_ISSUABLE_ASSIGNEE=
export DISCOTO_ISSUABLE_AUTHOR=
export DISCOTO_ISSUABLE_LABELS=discoto
[>>>] 
[>>>] Running tests on 19-quick_action_regex @ 7b9d9e350237c72b723c50303c200445a680e636
warning: parser/current is loading parser/ruby27, which recognizes
warning: 2.7.1-compliant syntax, but you are running 2.7.2.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
............................................

Finished in 2 minutes 27.6 seconds (files took 0.40726 seconds to load)
44 examples, 0 failures

Coverage report generated for RSpec to /home/james/ws/dev/gitlab/discussion-automation/coverage. 591 / 691 LOC (85.53%) covered.
[>>>] Cleaning up
[>>>] Cleaning up

Closes #19 (closed)