PEP 376 notice links to wrong canonical spec

On https://peps.python.org/pep-0376/ there's a notice that links to [Core metadata specifications](https://packaging.python.org/en/latest/specifications/core-metadata/#core-metadata). However, the spec that corresponds to this PEP is actually [Recording installed projects](https://packaging.python.org/en/latest/specifications/recording-installed-packages/).