Increasing perf swarming job expiration to 4 hours.

tools/perf/generate_perf_json.py

Index: tools/perf/generate_perf_json.py
diff --git a/tools/perf/generate_perf_json.py b/tools/perf/generate_perf_json.py
index 076cd80c5db98a49e00a572cbb57b38147dfd0a8..51c9bb98e443a8b7e935ac7fcbf43e45332828c6 100755
--- a/tools/perf/generate_perf_json.py
+++ b/tools/perf/generate_perf_json.py
@@ -305,6 +305,7 @@ def generate_telemetry_test(swarming_dimensions, benchmark_name, browser):
     # Always say this is true regardless of whether the tester
     # supports swarming. It doesn't hurt.
     'can_use_on_swarming_builders': True,
+    'expiration': 14400,
     'dimension_sets': swarming_dimensions
   }