Increase timeout for customer_testing test step (#154339)

Related: flutter/flutter#154251

Successful runs are bumping right up against the timeout

See https://ci.chromium.org/ui/p/flutter/builders/try/Linux%20customer_testing/84496/overview which succeeded in 29 minutes vs. https://ci.chromium.org/ui/p/flutter/builders/try/Linux%20customer_testing/84497/overview which failed with a timeout at 30 minutes.

Author: zanderso

.ci.yaml

@@ -487,19 +487,22 @@ targets:
       - .ci.yaml
 
   - name: Linux customer_testing
-    # TODO(matanlurey): https://github.com/flutter/flutter/issues/154293
+    # TODO(Piinks): https://github.com/flutter/flutter/issues/154251
     bringup: true
     # This really just runs dev/bots/customer_testing/ci.sh,
     # but it does so indirectly via the flutter_drone recipe
     # calling the dev/bots/test.dart script.
     enabled_branches:
       - master
     recipe: flutter/flutter_drone
+    # Timeout in minutes for the whole task.
     timeout: 60
     properties:
       shard: customer_testing
       tags: >
         ["framework", "hostonly", "shard", "linux"]
+      # Timeout in seconds for each individual step.
+      test_timeout_secs: "2700" # 45 minutes * 60
 
   - name: Linux docs_publish
     recipe: flutter/docs
@@ -3696,11 +3699,14 @@ targets:
     enabled_branches:
       - master
     recipe: flutter/flutter_drone
+    # Timeout in minutes for the whole task.
     timeout: 60
     properties:
       shard: customer_testing
       tags: >
         ["framework", "hostonly", "shard", "mac"]
+      # Timeout in seconds for each individual step.
+      test_timeout_secs: "2700" # 45 minutes * 60
 
   - name: Mac dart_plugin_registry_test
     recipe: devicelab/devicelab_drone
@@ -5363,11 +5369,14 @@ targets:
     enabled_branches:
       - master
     recipe: flutter/flutter_drone
+    # Timeout in minutes for the whole task.
     timeout: 60
     properties:
       shard: customer_testing
       tags: >
         ["framework", "hostonly", "shard", "windows"]
+      # Timeout in seconds for each individual step.
+      test_timeout_secs: "2700" # 45 minutes * 60
 
   - name: Windows framework_tests_libraries
     recipe: flutter/flutter_drone