Increase timeout for Linux web_tool_tests to 60m (flutter#162752)

flutter#162714

The "run test.dart for web_tool_tests" step is now taking longer than 30
minutes due to an increase in the number of tests.

## Pre-launch Checklist

- [X] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [X] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [X] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [X] I signed the [CLA].
- [X] I listed at least one issue that this PR fixes in the description
above.
- [X] I updated/added relevant documentation (doc comments with `///`).
- [ ] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [X] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [ ] All existing and new tests are passing.

Author: srujzs

.ci.yaml

@@ -2132,6 +2132,7 @@ targets:
         ["framework", "hostonly", "shard", "linux"]
       # Retry for flakes caused by https://github.com/flutter/flutter/issues/132654
       presubmit_max_attempts: "2"
+      test_timeout_secs: "3600" # https://github.com/flutter/flutter/issues/162714
     runIf:
       - dev/**
       - packages/flutter_tools/**