Revert "[X86][GlobalIsel] Support G_IS_FPCLASS" (#163792)

Reverts #162232 due to failures on EXPENSIVE_CHECKS enabled targets

Author: RKSimon

llvm/lib/Target/X86/GISel/X86LegalizerInfo.cpp

@@ -414,8 +414,6 @@ X86LegalizerInfo::X86LegalizerInfo(const X86Subtarget &STI,
 
   getActionDefinitionsBuilder(G_SEXT_INREG).lower();
 
-  getActionDefinitionsBuilder(G_IS_FPCLASS).lower();
-
   // fp constants
   getActionDefinitionsBuilder(G_FCONSTANT)
       .legalFor({s32, s64})