fix: removing a (maybe unnecessary) upstream request on group emission

[ozangunalp]

each emitted item already requests upstream items

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.13%. Comparing base (a1998df) to head (1a942f4).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2032      +/-   ##
============================================
- Coverage     89.18%   89.13%   -0.05%     
+ Complexity     3120     3119       -1     
============================================
  Files           412      412              
  Lines         13295    13294       -1     
  Branches       1688     1688              
============================================
- Hits          11857    11850       -7     
- Misses          812      815       +3     
- Partials        626      629       +3     

Files with missing lines	Coverage Δ
...mallrye/mutiny/operators/multi/MultiGroupByOp.java	86.08% <ø> (-0.07%)	⬇️

... and 10 files with indirect coverage changes

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[jponge]

It makes sense to me, I'd just add a test to make it obvious though 😃