doc: doc and test URLSearchParams discrepancy
The WHATWG URL spec is not going to change this behavior so let's document it
Fixes: https://github.com/nodejs/node/issues/33037
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines