tools: do not include docs in slim tarball

[aduh95]

Pulling and running doc-kit takes quite a long time (removing it cuts the make tar time to completion in half), when we don't really need it in test-shared.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.65%. Comparing base (0a9b67e) to head (457563c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62989      +/-   ##
==========================================
+ Coverage   89.64%   89.65%   +0.01%     
==========================================
  Files         707      707              
  Lines      219506   219509       +3     
  Branches    42087    42082       -5     
==========================================
+ Hits       196782   196810      +28     
+ Misses      14625    14588      -37     
- Partials     8099     8111      +12     

see 27 files with indirect coverage changes

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[panva]

RSLGTM