Fix CUDA 11.4.4 nightly in GitHub Actions (#3473)

Summary:
Pull Request resolved: https://github.com/facebookresearch/faiss/pull/3473

Previous diff (D57602154) fixed the CircleCI version and the PR build version of GHA but not the nightly one.

Reviewed By: junjieqi

Differential Revision: D57680576

fbshipit-source-id: 39f49c20df824c915f536b1ed3ffc35db2907988

.github/workflows/nightly.yml

@@ -25,6 +25,7 @@ jobs:
     runs-on: 4-core-ubuntu-gpu-t4
     env:
       CUDA_ARCHS: "60-real;61-real;62-real;70-real;72-real;75-real;80;86-real"
+      FAISS_FLATTEN_CONDA_INCLUDES: "1"
     steps:
       - name: Checkout
         uses: actions/checkout@v4