remove unused imports (1/3)

Summary:
Codehub raises unused imports as one of the most common issues in our codebase: https://fburl.com/quality/7w3p7qic
There is a codemod automation that finds and fixes these issues: https://fb.workplace.com/groups/pythonfoundation/permalink/2799727247007403/
I've run it with
```
$ ./python/libcst/libcst codemod remove_unused_imports.RemoveUnusedImportsWithGlean eden/mononoke
```
using a different directory in each diff
Then `arc lint` to fix autodeps where removing the imports removes a dependency.

*Impact*
A lot of these files are not used frequently, this cleanup still improves code legibility, solves possible naming issues, and potentially speeds up builds (I will not be measuring these).

Reviewed By: lmvasquezg

Differential Revision: D66874508

fbshipit-source-id: 4fee086907fb5ce62d43d2b159f522d200b4a3c6

eden/mononoke/tests/integration/integration_runner_real.py

@@ -16,7 +16,7 @@
 import sys
 import tempfile
 import xml.etree.ElementTree as ET
-from typing import Any, Dict, List, NamedTuple, Optional, Set
+from typing import Any, Dict, List, NamedTuple, Optional
 
 import click