Remove 118 CUDA run for GPU Unit Test CI (#3256)

Summary:
Pull Request resolved: #3256

CUDA 118 is too old - does not have updated references for FBGEMM anymore. Removing CUDA 118 case in GPU unit tests which was causing failures in OSS.

Note - there's an issue with other GPU unit tests - seems like timeout issue - I will resolve in separate diff.

Reviewed By: isururanawaka

Differential Revision: D79598741

fbshipit-source-id: d9efcfdeea08017f22631f229788f322db5d70fe

Author: aporialiao

.github/workflows/unittest_ci.yml

@@ -26,7 +26,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        cuda-tag: ["cu118", "cu126", "cu128"]
+        cuda-tag: ["cu126", "cu128"]
         os:
           - linux.g5.12xlarge.nvidia.gpu
         python:
@@ -43,8 +43,6 @@ jobs:
         is_pr:
           - ${{ github.event_name == 'pull_request' }}
         exclude:
-          - is_pr: true
-            cuda-tag: "cu118"
           - is_pr: true
             cuda-tag: "cu126"
           - is_pr: true