[Quantization] import torch.fx only if torch.__version__ >= 1.8

wanchen.swc

2023-03-30 0438b966d6d9ef89fdd7a8d112d6e03b34122b1e

 .github/workflows/main.yml

@@ -5,7 +5,7 @@
      - main
  push:
    branches:
      - dev
      - dev_wjm

jobs:
  docs: