[ONNX] Reduces onnx.Div sinceVersion to 7 (#3041)

The only difference between version 7 and newer versions is support for
different data types. We should allow this pattern to match as early as
7. Earlier versions have a more manual broadcast specification through
attributes, so I did not include those versions.

See: [onnx.Div
docs](https://onnx.ai/onnx/operators/onnx__Div.html#l-onnx-doc-divl)

lib/Conversion/TorchOnnxToTorch/DefaultDomainAtoF.cpp

@@ -1388,7 +1388,7 @@ void mlir::torch::onnx_c::populateDefaultDomainAtoF(
 
         return failure();
       });
-  patterns.onOp("Div", 14,
+  patterns.onOp("Div", 7,
                 [](OpBinder binder, ConversionPatternRewriter &rewriter) {
                   Torch::ValueTensorType resultType;
                   Value lhs, rhs;