Update detectron2 to fix Pillow errors (#1799)

Summary:
As reported in facebookresearch/detectron2#5010, `PIL.Image.LINEAR` no longer exists.

The Pillow requirement in `detectron2` isn't pinned, so old `detectron2` is installing the latest Pillow and causing errors in the TorchBench tests.

Pull Request resolved: #1799

Reviewed By: xuzhao9

Differential Revision: D47928411

Pulled By: msaroufim

fbshipit-source-id: 36fd447475c66c0db643b04cffd1fc8b5d4ca17f

Author: hmellor

torchbenchmark/util/framework/detectron2/requirements.txt

@@ -1,3 +1,3 @@
-git+https://github.com/facebookresearch/detectron2.git@c470ca3
+git+https://github.com/facebookresearch/detectron2.git@57bdb21
 omegaconf==2.1.1
 numpy