[ObjC] increase objc example build timeout to 1h (grpc#37747)

20min is often not enough to build these samples.

timeout log: https://btx.cloud.google.com/invocations/f48a9835-6e92-4651-b649-21a98a5dc0c3/targets

Closes grpc#37747

COPYBARA_INTEGRATE_REVIEW=grpc#37747 from HannahShiSFB:bump-build-objc-example-timeout 8f2f027
PiperOrigin-RevId: 676042240

tools/run_tests/run_tests.py

@@ -1113,7 +1113,7 @@ def test_specs(self):
         out.append(
             self.config.job_spec(
                 ["src/objective-c/tests/build_one_example.sh"],
-                timeout_seconds=20 * 60,
+                timeout_seconds=60 * 60,
                 shortname="ios-buildtest-example-sample",
                 cpu_cost=1e6,
                 environ={
@@ -1126,7 +1126,7 @@ def test_specs(self):
         out.append(
             self.config.job_spec(
                 ["src/objective-c/tests/build_one_example.sh"],
-                timeout_seconds=20 * 60,
+                timeout_seconds=60 * 60,
                 shortname="ios-buildtest-example-switftsample",
                 cpu_cost=1e6,
                 environ={
@@ -1138,7 +1138,7 @@ def test_specs(self):
         out.append(
             self.config.job_spec(
                 ["src/objective-c/tests/build_one_example.sh"],
-                timeout_seconds=20 * 60,
+                timeout_seconds=60 * 60,
                 shortname="ios-buildtest-example-switft-use-frameworks",
                 cpu_cost=1e6,
                 environ={