Improve `pathname2url()` and `url2pathname()` docs #133635

Job	Run time
Change detection / Compute changed files	9s
Windows ${{ ((fromJSON(matrix.free-threading) && '(free-threading)') \|\| '') }}	0s
Check if Autoconf files are up to date	0s
Check if generated files are up to date	0s
macOS ${{ ((fromJSON(matrix.free-threading) && '(free-threading)') \|\| '') }}	0s
Ubuntu ${{ ((fromJSON(matrix.free-threading) && '(free-threading)') \|\| '') }}	0s
Windows MSI${{ '' }}	0s
Thread sanitizer	0s
Address sanitizer	0s
Ubuntu SSL tests with OpenSSL	0s
WASI	0s
Hypothesis tests on Ubuntu	0s
Thread sanitizer (free-threading)	0s
CIFuzz	0s
Docs / Doctest	4m 34s
Docs / Docs	2m 6s
Docs / Docs (Oldest Sphinx)	2m 17s
All required checks pass	2s
	9m 8s

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