Fix arrow groupby na #21810

Job	Run time
Pyodide build	25m 48s
Linux-32-bit	18m 15s
Linux-Musl	16m 0s
python-freethreading	24m 24s
python-dev (macOS-13)	23m 14s
python-dev (macOS-14)	12m 41s
python-dev (ubuntu-22.04)	21m 4s
python-dev (windows-latest)	24m 21s
macos-13 actions-310.yaml	33m 22s
macos-13 actions-311.yaml	43m 9s
macos-13 actions-312.yaml	33m 51s
macos-14 actions-310.yaml	23m 20s
macos-14 actions-311.yaml	25m 37s
macos-14 actions-312.yaml	24m 4s
windows-latest actions-311.yaml	42m 54s
windows-latest actions-312.yaml	52m 50s
windows-latest actions-310.yaml	43m 31s
Minimum Versions	25m 24s
Future infer strings (without pyarrow)	46m 50s
Locale: zh_CN	29m 3s
Locale: it_IT	29m 12s
Downstream Compat	6m 48s
Numpy Dev	17m 47s
Pyarrow Nightly	21m 15s
Future infer strings	57m 15s
Pypy	3m 45s
ubuntu-22.04 actions-310.yaml	54m 13s
ubuntu-22.04 actions-311.yaml	50m 41s
ubuntu-22.04 actions-312.yaml	54m 40s
ubuntu-24.04-arm actions-311.yaml	25m 56s
ubuntu-24.04-arm actions-312.yaml	27m 25s
ubuntu-24.04-arm actions-310.yaml	23m 37s
	16h 2m 16s

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