Update pytorch pin to 2024/03/21 nightly (#2562)

Summary:
Pull Request resolved: #2562

## Context

Update PyTorch nightly pin to 2024/03/21. Note that as of 2024/03/20 PyTorch version has been bumped to `2.4.0` (from `2.3.0`) and torchvision has been bumped to `0.19.0` (from `0.18.0`).

imported-using-ghimport

Test Plan: Imported from OSS

Reviewed By: JacobSzwejbka, angelayi

Differential Revision: D55198673

Pulled By: SS-JIA

fbshipit-source-id: e49cf17fdc5e22fac2712ac6f05815f2b9264091

Author: SS-JIA

.ci/docker/ci_commit_pins/pytorch.txt

@@ -1 +1 @@
-6ca9ae4f8693639c395544327f7e362441a58c79
+ef0d470eb372a5e68f6332bea9b1df26fca28b59

install_requirements.sh

@@ -49,12 +49,12 @@ done
 # models in executorch/examples/models.
 # The version in this file will be the correct version for the
 # corresponsing version of the repo.
-NIGHTLY_VERSION=dev20240312
+NIGHTLY_VERSION=dev20240322
 
-TORCH_VERSION=2.3.0.${NIGHTLY_VERSION}
+TORCH_VERSION=2.4.0.${NIGHTLY_VERSION}
 pip install --force-reinstall --pre torch=="${TORCH_VERSION}" -i https://download.pytorch.org/whl/nightly/cpu
 
-TORCH_VISION_VERSION=0.18.0.${NIGHTLY_VERSION}
+TORCH_VISION_VERSION=0.19.0.${NIGHTLY_VERSION}
 pip install --force-reinstall --pre torchvision=="${TORCH_VISION_VERSION}" -i https://download.pytorch.org/whl/nightly/cpu
 
 TORCH_AUDIO_VERSION=2.2.0.${NIGHTLY_VERSION}