Update torch pin (9/20) (#407)

Summary:
Pull Request resolved: #407

#392

Reviewed By: mergennachin, kimishpatel

Differential Revision: D49399549

fbshipit-source-id: fb6c2d1e8f12ffb0b4496cc6a8d39235ca0b0e25

Author: angelayi

.ci/docker/ci_commit_pins/nightly.txt

@@ -1 +1 @@
-dev20230912
+dev20230920

install_requirements.sh

@@ -17,7 +17,7 @@ pip install .
 # models in executorch/examples/models.
 # The version in this file will be the correct version for the
 # corresponsing version of the repo.
-NIGHTLY_VERSION=dev20230912
+NIGHTLY_VERSION=dev20230920
 
 TORCH_VERSION=2.2.0.${NIGHTLY_VERSION}
 pip install --force-reinstall --pre torch=="${TORCH_VERSION}" -i https://download.pytorch.org/whl/nightly/cpu