[ci] Update github action for v26.06

Author: epernod

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-22.04, macos-14, windows-2022]
-        sofa_branch: [master]
+        sofa_branch: [v26.06]
 
     steps:
       # https://github.com/actions/runner-images/issues/6817