test: increase timeout on benchmarks

With having more benchmarks, we started hitting the 600s pytest timeout:
https://buildkite.com/firecracker/firecracker-pr-optional/builds/9105.
Increase it to 900s.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

tests/integration_tests/performance/test_benchmarks.py

@@ -17,7 +17,7 @@
 
 
 @pytest.mark.no_block_pr
-@pytest.mark.timeout(600)
+@pytest.mark.timeout(900)
 def test_no_regression_relative_to_target_branch():
     """
     Run the microbenchmarks in this repository, comparing results from pull