Sam is Acting PM for Growth:Expansion

Why is this change being made?

Sam is Acting PM for Growth:Expansion. This updates team.yml to reflect that change (replacing Tim's entry), without altering Sam's existing entry as Conversion PM.

this change will be reflected in:

1. the org chart https://about.gitlab.com/company/team/org-chart/ -> https://growth-expansion-acting-pm.about.gitlab-review.app/company/team/org-chart/
2. team lists, e.g. https://about.gitlab.com/handbook/engineering/development/growth/expansion/#group-members -> https://growth-expansion-acting-pm.about.gitlab-review.app/handbook/engineering/development/growth/expansion/#group-members

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the "Maintained by" section in on the page being edited.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies.
  • If the changes relate to any part of the project other than updates to content and/or data files please make sure to ping @gl-static-site-editor in a comment for a review and merge. For example changes to .gitlab-ci.yml, JavaScript/CSS/Ruby code or the layout files. (this requirement has been removed pending identification of a new DRI for the handbook)