BUG: Fix unpickling of string dtypes of legacy pandas versions #24265

Job	Run time
python-dev	-1s
Linux-32-bit	18m 49s
Linux-Musl	14m 54s
Pyodide build	23m 5s
windows-latest actions-312.yaml	38m 45s
macos-13 actions-313.yaml	34m 35s
macos-14 actions-310.yaml	20m 45s
windows-latest actions-310.yaml	40m 4s
macos-14 actions-313.yaml	21m 15s
macos-14 actions-312.yaml	17m 15s
windows-latest actions-313.yaml	43m 35s
macos-14 actions-311.yaml	17m 14s
macos-13 actions-311.yaml	32m 8s
macos-13 actions-310.yaml	33m 13s
windows-latest actions-311.yaml	37m 15s
ubuntu-24.04 actions-312.yaml	42m 57s
macos-13 actions-312.yaml	36m 0s
ubuntu-24.04-arm actions-310.yaml	36m 48s
ubuntu-24.04-arm actions-313.yaml	36m 58s
ubuntu-24.04 actions-311.yaml	41m 57s
Future infer strings	45m 31s
ubuntu-24.04 actions-313.yaml	49m 5s
Downstream Compat	6m 8s
Locale: zh_CN	24m 2s
Freethreading	22m 8s
Locale: it_IT	23m 59s
Future infer strings (without pyarrow)	39m 4s
ubuntu-24.04-arm actions-311.yaml	36m 3s
ubuntu-24.04-arm actions-312.yaml	35m 42s
Numpy Dev	17m 19s
ubuntu-24.04 actions-310.yaml	47m 14s
Pypy	1m 50s
Minimum Versions	23m 20s
Pyarrow Nightly	20m 6s
	16h 19m 2s

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