[BUG] Fix concat expression typing

[colin-ho]

#2863

[codspeed-hq]

CodSpeed Performance Report

Merging #2868 will degrade performances by 52.51%

_{Comparing colin/fix-concat-expr (ff7b050) with main (78a92a2)}

Summary

❌ 3 regressions
✅ 13 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	colin/fix-concat-expr	Change
❌	test_count[1 Small File]	9.9 ms	16.7 ms	-40.4%
❌	test_explain[100 Small Files]	33 ms	69.5 ms	-52.51%
❌	test_show[100 Small Files]	257.9 ms	315.1 ms	-18.16%

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.93%. Comparing base (7ee5fda) to head (ff7b050).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2868      +/-   ##
==========================================
+ Coverage   64.12%   65.93%   +1.80%     
==========================================
  Files        1008     1010       +2     
  Lines      115728   113441    -2287     
==========================================
+ Hits        74215    74801     +586     
+ Misses      41513    38640    -2873     

Flag	Coverage Δ
	65.93% <100.00%> (?)

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

Files with missing lines	Coverage Δ
daft/expressions/expressions.py	93.37% <100.00%> (-0.13%)	⬇️

... and 77 files with indirect coverage changes