Update documentation for PackageLocation to clarify that the package path needs to _end with_ the package.
Update documentation for PackageLocation to clarify that the package path needs
to _end with_ the package.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=157864018

cushon/error-prone,google/error-prone,cushon/error-prone,google/error-prone,cushon/error-prone,cushon/error-prone