test_datetimes.py: fix literal string #21694

Job	Run time
Pyodide build	25s
Linux-32-bit	25s
Linux-Musl	25s
python-freethreading	26s
python-dev (macOS-13)	26s
python-dev (macOS-14)	27s
python-dev (ubuntu-22.04)	25s
python-dev (windows-latest)	23s
macos-13 actions-310.yaml	25s
macos-13 actions-311.yaml	25s
macos-13 actions-312.yaml	24s
macos-14 actions-310.yaml	25s
macos-14 actions-311.yaml	24s
macos-14 actions-312.yaml	24s
windows-latest actions-311.yaml	24s
windows-latest actions-312.yaml	23s
windows-latest actions-310.yaml	23s
Minimum Versions	27s
Future infer strings (without pyarrow)	26s
Locale: zh_CN	25s
Locale: it_IT	26s
Downstream Compat	26s
Numpy Dev	25s
Pyarrow Nightly	25s
Pypy	26s
Future infer strings	7s
ubuntu-22.04 actions-310.yaml	26s
ubuntu-22.04 actions-311.yaml	24s
ubuntu-22.04 actions-312.yaml	24s
ubuntu-24.04-arm actions-311.yaml	26s
ubuntu-24.04-arm actions-312.yaml	25s
ubuntu-24.04-arm actions-310.yaml	23s
	13m 0s

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