fx quant: rename matches -> is_match (#43914)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43914
Renames `matches` function to `is_match`, since there is also
a list named `matches` we are passing around in `Quantizer`,
and would be good to decrease name conflicts.
Test Plan:
```
python test/test_quantization.py TestQuantizeFxOps
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D23435601
fbshipit-source-id: 394af11e0120cfb07dedc79d5219247330d4dfd6
