Increase sub-task timeout for `Mac web_tool_tests`

.ci.yaml

diff --git a/.ci.yaml b/.ci.yaml
index b7faa06..c935af1 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -4702,7 +4702,7 @@
       subshard: "1_1"
       tags: >
         ["framework", "hostonly", "shard", "mac"]
-      test_timeout_secs: "2700" # Allows 45 minutes (up from 30 default)
+      test_timeout_secs: "3600" # 60 minutes to match the global `timeout` property.
     runIf:
       - dev/**
       - packages/flutter_tools/**