ci: disable tests in Vulkan build with default Ubuntu packages

Author: mbaudier

.github/workflows/build.yml

@@ -420,15 +420,6 @@ jobs:
         run: |
           cmake --build build -j $(nproc)
 
-      - name: Test
-        id: cmake_test
-        run: |
-          cd build
-          export GGML_VK_VISIBLE_DEVICES=0
-          export GGML_VK_DISABLE_F16=1
-          # This is using llvmpipe and runs slower than other backends
-          ctest -L main --verbose --timeout 4200
-
   ubuntu-24-cmake-vulkan:
     runs-on: ubuntu-24.04