add T2w to suffix allowlist

[harrisonritz]

PR Description

Hi, first time PR.
Very minor, just add T2w to suffix allowlist. Arose by following laMEG recommendations.
Didn't add test because it's so minor. Feel free to decide whether I should be added to authors.

Merge checklist

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If applicable:

• All comments are resolved
• This is not your own PR
• All CIs are happy
• PR title starts with [MRG]
• whats_new.rst is updated
• New contributors have been added to CITATION.cff
• PR description includes phrase "closes <#issue-number>"

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.46%. Comparing base (23e4b99) to head (bd2c847).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1420   +/-   ##
=======================================
  Coverage   97.46%   97.46%           
=======================================
  Files          40       40           
  Lines        9096     9096           
=======================================
  Hits         8865     8865           
  Misses        231      231           

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[sappelhoff]

LGTM thanks @harrisonritz!

[welcome]

🎉 Congrats on merging your first pull request! 🥳 Looking forward to seeing more from you in the future! 💪