upgrade to flash-attn 2.8.0.post2 (#2828)

* upgrade to flash-attn 2.8.0.post2

* use cu126 with torch 2.6

* seems vllm 0.8.5.post1 not compatible with cuda12.6.3 and torch 2.6

* cu126 + torch 2.6 as the default

* use cu126 for multigpu w torch 2.6 too

* drop vllm for now from ci for now

.github/workflows/multi-gpu-e2e.yml

@@ -26,11 +26,11 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - cuda: 124
-            cuda_version: 12.4.1
+          - cuda: 126
+            cuda_version: 12.6.3
             python_version: "3.11"
             pytorch: 2.6.0
-            axolotl_extras: vllm
+            axolotl_extras:
             num_gpus: 2
             nightly_build: "true"
           - cuda: 124