Remove haskell-suite-dummy-program hack

There was some hacky logic in place to give a "haskell-suite" compiler
a dummy location so that we would attempt to configure it.

This logic is no longer necessary since 'configureRequiredProgram' was
changed to accomodate the situation in which 'lookupKnownProgram' fails.
In fact, it is downright harmful, as this dummy location will trigger
errors when we attempt to configure all known programs, which is
a necessary step before attempting to serialise a program database.