Drop support for python3.6 as per task T109096383. Item 2 on issue 2051. (#2119)

Summary:
As per item 2 on [issue 2051](https://github.com/pytorch/audio/issues/2051), dropping support for python 3.6.
Removed 3.6 from test matrix and ran `.circleci/regenerate.py `.

Pull Request resolved: https://github.com/pytorch/audio/pull/2119

Reviewed By: mthrok

Differential Revision: D33379542

Pulled By: wernerchao

fbshipit-source-id: 6d0fb51b18c2fa7c8cf4eeee4a7f19c4a5210fac

.circleci/regenerate.py

@@ -21,7 +21,7 @@ import yaml
 from jinja2 import select_autoescape
 
 
-PYTHON_VERSIONS = ["3.6", "3.7", "3.8", "3.9"]
+PYTHON_VERSIONS = ["3.7", "3.8", "3.9"]
 CU_VERSIONS_DICT = {
     "linux": ["cpu", "cu102", "cu111", "cu113", "cu115", "rocm4.1"],
     "windows": ["cpu", "cu113", "cu115"],