[ValueTracking] Remove ORE argument (NFC-ish)

The ORE argument threaded through ValueTracking is used only in a
single, untested place. It is also essentially never passed: The
only places that do so have been added very recently as part of the
KnownFPClass migration, which is vanishingly unlikely to hit this
code path. Remove this effectively dead argument.

Differential Revision: https://reviews.llvm.org/D151562