[DOCS] Update Iceberg roadmap on docs

[kevinzwang]

No description provided.

[kevinzwang]

Where can I see the generated docs?

[codspeed-hq]

CodSpeed Performance Report

Merging #3240 will not alter performance

_{Comparing kevin/iceberg-roadmap-docs (40f147a) with main (61b6842)}

Summary

✅ 17 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.95%. Comparing base (61b6842) to head (40f147a).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3240      +/-   ##
==========================================
- Coverage   79.13%   78.95%   -0.18%     
==========================================
  Files         637      637              
  Lines       77993    78490     +497     
==========================================
+ Hits        61719    61974     +255     
- Misses      16274    16516     +242     

see 11 files with indirect coverage changes