test_datetimes.py: fix literal string (#60820) #43218

Job	Run time
Test Conda Forge Recipe - Python 3.11	2m 4s
Test Conda Forge Recipe - Python 3.10	2m 16s
Install Extras - all	5m 16s
Install Extras - clipboard	4m 30s
Install Extras - aws	4m 33s
Install Extras - compression	4m 32s
Install Extras - computation	4m 36s
Install Extras - feather	4m 54s
Install Extras - excel	4m 35s
Install Extras - hdf5	4m 32s
Install Extras - gcp	4m 32s
Install Extras - fss	4m 30s
Install Extras - html	4m 47s
Install Extras - mysql	4m 30s
Install Extras - output-formatting	4m 33s
Install Extras - parquet	4m 25s
Install Extras - performance	4m 40s
Install Extras - plot	4m 36s
Install Extras - postgresql	4m 35s
Install Extras - spss	4m 24s
Install Extras - pyarrow	4m 44s
Install Extras - sql-other	4m 39s
Install Extras - test	4m 31s
Install Extras - xml	4m 31s
	1h 45m 45s

Provide feedback