cmake: Update vllm_flash_attn for vllm_kernels (#20032)

Signed-off-by: Eli Uriegas <eliuriegas@meta.com>

Author: seemethere

cmake/external_projects/vllm_flash_attn.cmake

@@ -38,7 +38,7 @@ else()
   FetchContent_Declare(
           vllm-flash-attn
           GIT_REPOSITORY https://github.com/vllm-project/flash-attention.git
-          GIT_TAG 2c6bcfc0feb3d9d4a57b243fc159a68aa9933f5b
+          GIT_TAG 5f3644181c7a15345ce20bfc65af117d3601b524
           GIT_PROGRESS TRUE
           # Don't share the vllm-flash-attn build between build types
           BINARY_DIR ${CMAKE_BINARY_DIR}/vllm-flash-attn