Update crate keywords

[Philippe-Cholet]

Now that group_by has been renamed to chunk_by in #866 I think we should just delete the crate keyword "group-by".
Note that on crates.io, this keyword only leads to "itertools" and "itertools-wild" so it does not seem useful at all.

Should we delete another one as well?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6814180) 94.38% compared to head (8697d15) 94.37%.
Report is 10 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #879      +/-   ##
==========================================
- Coverage   94.38%   94.37%   -0.01%     
==========================================
  Files          48       48              
  Lines        6665     6672       +7     
==========================================
+ Hits         6291     6297       +6     
- Misses        374      375       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[jswrenn]

Sounds reasonable to me. I doubt "group-by" is even that common of a search term.