[AIRFLOW-XXXX] Update GitLab team members

[tayloramurphy]

@tlapiana is no longer with the company and @m_walker is new on the team!

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Issue link: Document only change, no JIRA issue

Make sure to mark the boxes below before creating PR: [x]

• Description above provides context of the change
• Commit message/PR title starts with [AIRFLOW-NNNN]. AIRFLOW-NNNN = JIRA ID^*
• Unit tests coverage for changes (not needed for documentation changes)
• Commits follow "How to write a good git commit message"
• Relevant documentation is updated including usage instructions.
• I will engage committers as explained in Contribution Workflow Example.

^* For document-only changes commit message can start with [AIRFLOW-XXXX].

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In case of backwards incompatible changes please leave a note in UPDATING.md.
Read the Pull Request Guidelines for more information.

[tayloramurphy]

My apologies for not setting things up properly!! Thanks for the fix ❤️