Remove social share links for annotations and groups

[acelaya]

Our social share links are outdated (among other things, the Twitter one is still using the old brand icon), and we suspect they are barely used, so this PR removes them from both the annotation and group sharing dialogs.

Before:

After:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.45%. Comparing base (b3d30d9) to head (92b5223).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7160      +/-   ##
==========================================
- Coverage   99.45%   99.45%   -0.01%     
==========================================
  Files         271      270       -1     
  Lines       10965    10958       -7     
  Branches     2624     2623       -1     
==========================================
- Hits        10905    10898       -7     
  Misses         60       60              

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[robertknight]

LGTM. As a note for the future, we discussed using the Web Share API as a more device/platform-aware alternative to these in future.