Update nightly version, 9/12 (#283)

Summary:
Pull Request resolved: #283

Cutting stable branch cut. Update nightly

Reviewed By: guangy10

Differential Revision: D49188831

fbshipit-source-id: f1803aed7d103d26c5f9464976ac494b9b491310

Author: mergennachin

.ci/docker/ci_commit_pins/nightly.txt

@@ -1 +1 @@
-dev20230908
+dev20230912

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=dev20230908
+NIGHTLY_VERSION=dev20230912
 
 TORCH_VERSION=2.2.0.${NIGHTLY_VERSION}
 pip install --force-reinstall --pre torch=="${TORCH_VERSION}" -i https://download.pytorch.org/whl/nightly/cpu