[MLIR][OpenMP] NFC: Remove redundant check (#91594)

The check removed by this patch in the OpenMP to LLVM IR translation
pass already exists as part of the op verifier for `omp.loop_nest`.

Author: skatrak

mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp

@@ -939,10 +939,6 @@ convertOmpWsloop(Operation &opInst, llvm::IRBuilderBase &builder,
   llvm::ArrayRef<bool> isByRef = getIsByRef(wsloopOp.getReductionVarsByref());
   assert(isByRef.size() == wsloopOp.getNumReductionVars());
 
-  // TODO: this should be in the op verifier instead.
-  if (loopOp.getLowerBound().empty())
-    return failure();
-
   // Static is the default.
   auto schedule =
       wsloopOp.getScheduleVal().value_or(omp::ClauseScheduleKind::Static);