Increased expiration_time to 4 hrs

There are still purple builds for fyi/ios12-sdk-simulators
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/ios12-sdk-simulator

Bug: 933450
Change-Id: If1bdc09f9a8c4dc0d5665eeb1e40ecd927814980
Reviewed-on: https://chromium-review.googlesource.com/c/1490393Reviewed-by: Justin Cohen <justincohen@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Maksym Onufriienko <monufriienko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635825}

ios/build/bots/chromium.fyi/ios12-sdk-simulator.json

@@ -21,7 +21,7 @@
     "all"
   ],
   "configuration": "Debug",
-  "expiration_time": 10800,
+  "expiration_time": 14400,
   "tests": [
     {
       "xcode parallelization": true,