Support newlines for the chatops "run" command

What does this MR do?

Support newlines for the chatops "run" command

We ran into this as part of gitlab-com/gl-infra/delivery#1622 (closed). By enabling the /m mode, the dot operator matches newlines. This allows the use of newlines when using the "run" command.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because _____.
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content