### Description
- Fix quantization tool bug that did not correctly set a quantized
bias's scale data type to fp16 if the original bias was fp16.
- Enabled fp16 ConvTranspose quantization unit tests that were disabled.
### Motivation and Context
Python quantization tests for fp16 ConvTranspose were originally
disabled due to a shape inference bug. It turns out that we also have a
bug in our quantizer that does not properly handle fp16 bias inputs.
Fixing the bug allows us to re-enable these tests with the latest
version of ONNX.