tSNE components parameter

[ch1ru]

Added the n_components parameter in the tsne function, similar to the one in umap and updated docstring.

• Closes Additional parameters in some functions - new functions #460
• Tests included or not required because: Not included but can add tests if necessary.

• Release notes not necessary because: Only minor change.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.84%. Comparing base (c410cd1) to head (88d721c).
Report is 76 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2803   +/-   ##
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  Coverage   72.84%   72.84%           
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  Files         111      111           
  Lines       12368    12368           
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  Hits         9009     9009           
  Misses       3359     3359           

Files	Coverage Δ
scanpy/tools/_tsne.py	90.69% <ø> (ø)