Code-Quality: automatically clean-up container after it has run

What does this MR do?

Adds the --rm option to docker run in Code-Quality.gitlab-ci.yml such that the code quality container is automatically cleaned up after it has run.

This addresses issue #335963 (closed) whereby the temporary containers used by the Code-Quality template are not removed after job, for example when using dedicated gitlab-runner without docker-in-docker.

Screenshots or Screencasts (strongly suggested)

N/A

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
  • I don't think this needs a changelog
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
  • I don't think this has any performance impact.
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.
  • I think it is fine. Feel free to correct me if that's not the case.

Availability and Testing

⚠ DISCLAIMER ⚠ : I have not tested this change myself. As a simple gitlab user, I do not have the ability to build my own gitlab in a test environment for testing. This proposed change is my best guess about how to solve issue #335963 (closed) but should be reviewed by code owners.

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.