[EZ][BE] Fix ResourceWarning (#120886)
By closing the file handle
Fixes
```
/Users/nshulga/git/pytorch/pytorch/test/quantization/core/test_docs.py:132: ResourceWarning: unclosed file <_io.TextIOWrapper name='/Users/nshulga/git/pytorch/pytorch/docs/source/quantization.rst' mode='r' encoding='UTF-8'>
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120886
Approved by: https://github.com/seemethere, https://github.com/kit1980, https://github.com/Skylion007
