fix: fix in-correct unittest (pk infer)

[BowenXiao1999]

What's changed and what's your intention?

The source has pk vec![2]. So the agg should accept pk_indices as vec![2].

The unitest is wrong-written.

Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests
• All checks passed in ./risedev check (or alias, ./risedev c)

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

Merging #3192 (c827d41) into main (921fc59) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #3192   +/-   ##
=======================================
  Coverage   73.58%   73.58%           
=======================================
  Files         744      744           
  Lines      102198   102198           
=======================================
+ Hits        75200    75203    +3     
+ Misses      26998    26995    -3     

Flag	Coverage Δ
rust	73.58% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
src/stream/src/executor/global_simple_agg.rs	96.08% <100.00%> (ø)
src/stream/src/executor/hash_agg.rs	97.62% <100.00%> (ø)
src/common/src/types/ordered_float.rs	24.90% <0.00%> (+0.19%)	⬆️
src/stream/src/executor/aggregation/mod.rs	95.73% <0.00%> (+0.77%)	⬆️

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