TST: update expected dtype for sum of decimals with pyarrow 21+ #24319

Job	Run time
Linux-Musl	15m 38s
Linux-32-bit	18m 39s
python-dev	0s
Pyodide build	23m 30s
windows-latest actions-313.yaml	40m 55s
macos-14 actions-310.yaml	26m 47s
macos-14 actions-311.yaml	20m 18s
windows-latest actions-312.yaml	35m 12s
macos-13 actions-313.yaml	28m 41s
macos-14 actions-312.yaml	22m 11s
macos-13 actions-310.yaml	33m 31s
windows-latest actions-311.yaml	34m 19s
ubuntu-24.04-arm actions-310.yaml	37m 4s
macos-13 actions-311.yaml	32m 10s
macos-14 actions-313.yaml	27m 21s
windows-latest actions-310.yaml	34m 32s
ubuntu-24.04-arm actions-311.yaml	35m 31s
Future infer strings	44m 2s
macos-13 actions-312.yaml	30m 34s
ubuntu-24.04 actions-313.yaml	47m 50s
ubuntu-24.04 actions-310.yaml	48m 18s
Freethreading	21m 13s
Pyarrow Nightly	19m 56s
ubuntu-24.04-arm actions-313.yaml	36m 24s
Minimum Versions	23m 13s
Future infer strings (without pyarrow)	39m 29s
ubuntu-24.04 actions-312.yaml	43m 25s
ubuntu-24.04 actions-311.yaml	41m 29s
Numpy Dev	16m 21s
ubuntu-24.04-arm actions-312.yaml	36m 42s
Locale: it_IT	24m 28s
Downstream Compat	5m 22s
Locale: zh_CN	23m 39s
Pypy	1m 36s
	16h 10m 20s

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