pythongh-132912: Set 15 min timeout on GHA Hypothesis CI (pythonGH-132914)

(cherry picked from commit eb2e430)

Co-authored-by: Victor Stinner <[email protected]>

Author: vstinner

.github/workflows/build.yml

@@ -457,8 +457,9 @@ jobs:
         # failing when executed from inside a virtual environment.
         "${VENV_PYTHON}" -m test \
           -W \
-          -o \
+          --slowest \
           -j4 \
+          --timeout 900 \
           -x test_asyncio \
           -x test_multiprocessing_fork \
           -x test_multiprocessing_forkserver \