Resize team images from 240x240 to 120x120

Why is this change being made?

Team images are currently resized to 240x240, but they are only used at 120x120. This results in a bigger file size that causes longer page load times. This MR updates the bin/crop-team-pictures script to size them to the correct file use size.

The result is a slight reduction in the resources downloaded to view the page. <!29388 Provide a detailed answer to question on why this change is being proposed, in accordance with our value of [Transparency][transparency]. -->

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][transparency]
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to your manager.
  • 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][mr-buddies-slack].
  • 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.

Related #8146 (closed)