[MLIR][Tensor] Remove assert in PadOp builder

[chelini]

Summary

The assert is misplaced as the result type is allowed to be null. A few
lines below the result type is inferred if it is passed a nullptr.
Besides, this behavior is described in the documentation of the builder.

[ftynse]

I suppose the intention was to check that the type is a ranked type when it is actually provided. This builder delegates to another, which does a cast that will assert, so there is no extra benefit in having this one.

mlir/lib/Dialect/Tensor/IR/TensorOps.cpp

void PadOp::build(OpBuilder &b, OperationState &result, Value source,
   build(b, result, source, staticVector, staticVector, low, high, nofold,
         attrs);
 }
 
 void PadOp::build(OpBuilder &b, OperationState &result, Type resultType,
                   Value source, ArrayRef<OpFoldResult> low,
                   ArrayRef<OpFoldResult> high, bool nofold,
                   ArrayRef<NamedAttribute> attrs) {
-  assert(resultType.isa<RankedTensorType>());
   auto sourceType = source.getType().cast<RankedTensorType>();
   SmallVector<Value, 4> dynamicLow, dynamicHigh;
   SmallVector<int64_t, 4> staticLow, staticHigh;
   // staticLow and staticHigh have full information of the padding config.
   // This will grow staticLow and staticHigh with 1 value. If the config is
   // dynamic (ie not a constant), dynamicLow and dynamicHigh will grow with 1
   // value as well.
   dispatchIndexOpFoldResults(low, dynamicLow, staticLow,