MNT Fixes packaging for flyteidl wheel

[thomasjpfan]

Tracking issue

Follow up to #4799

Why are the changes needed?

This PR fixes the pyproject.toml when building the wheel.

How was this patch tested?

Run python -m build and unzip the wheel in dist/ to see the contents.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6a2ce3f) 58.97% compared to head (0a556a0) 59.66%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4846      +/-   ##
==========================================
+ Coverage   58.97%   59.66%   +0.69%     
==========================================
  Files         644      644              
  Lines       55146    49521    -5625     
==========================================
- Hits        32521    29549    -2972     
+ Misses      20050    17398    -2652     
+ Partials     2575     2574       -1     

Flag	Coverage Δ
unittests	59.34% <ø> (+0.37%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

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