Increase build-test-gpu timeout to 8h (#3840)

To address timeouts on some hardware

Author: kwasd

.github/workflows/build-test-gpu.yml

@@ -49,6 +49,7 @@ permissions: read-all
 jobs:
   integration-tests:
     name: Integration tests matrix
+    timeout-minutes: 480
     strategy:
       matrix:
         python: ["3.9"]