docs(sphinx): fix links to reverse flags when using the :ghc-flag:`-fno-<flag>` syntax

Zubinrequested to merge
wip/26352 into master

docs(sphinx): fix links to reverse flags when using the :ghc-flag:-fno-<flag> syntax

This solution is rather hacky and I suspect there is a better way to do this but I don't know enough about Sphinx to do better.

Fixes #26352 (closed)

Merge request reports