update torch pin (#2944)

Summary:
Pull Request resolved: #2944

Need change from D55354487 to get mutable buffer + pt2e working

Reviewed By: JacobSzwejbka

Differential Revision: D55922254

Author: cccclai

install_requirements.sh

@@ -61,7 +61,7 @@ done
 # NOTE: If a newly-fetched version of the executorch repo changes the value of
 # NIGHTLY_VERSION, you should re-run this script to install the necessary
 # package versions.
-NIGHTLY_VERSION=dev20240324
+NIGHTLY_VERSION=dev20240406
 
 # The pip repository that hosts nightly torch packages.
 TORCH_NIGHTLY_URL="https://download.pytorch.org/whl/nightly/cpu"