crosperf: Add retries to nightly loading.desktop

Test results are very flaky in nightly tests.
In contrast loading.desktop in telemetry_AFDOGenerate is much more
stable where the test has 1 retry.

Retries can significantly extend the test duration but it shouldn't be a
problem since tests are running only every second day and usually take
less than 12h.

BUG=b:229477430
TEST=cq

Change-Id: I0a7ad0cb68359a8844ba9804ad232060498a58a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/4024307
Commit-Queue: Denis Nikitin <denik@chromium.org>
Tested-by: Denis Nikitin <denik@chromium.org>
Reviewed-by: Jordan Abrahams-Whitehead <ajordanr@google.com>
diff --git a/buildbot_test_toolchains.py b/buildbot_test_toolchains.py
index 19c31b5..e847af4 100755
--- a/buildbot_test_toolchains.py
+++ b/buildbot_test_toolchains.py
@@ -178,7 +178,6 @@
       test_args: --story-tag-filter=typical
       iterations: 3
       run_local: False
-      retries: 0
     }
     """