This entry in `.codeqlmanifest.json` was intended to allow
unpacking the CodeQL CLI as a subdirectory of `ql`, and things
would Just Work.
However, it is not necessary anymore because recent releases of
the CLI will search their own directory as a fallback
_independently_ of the parent directory.
On the contrary, removing this link will make internal testing
easier because you then run a test build of the CLI with
`--search-path` pointing to the `ql` checkout without inadvertently
making extractors in a _different_ build that is unpacked there visible.