Android perf tests shards 20->6 (only --smoke-test-mode)

try 4470:
Max shard runtime (5m 14s) + overhead (19s): 5m 34s (shard #2)
Min shard runtime (4m 41s) + overhead (10s): 4m 51s (shard #1)
Total shard runtime (29m 21s) + overhead(1m 37s): 30m 58s

Bug: angleproject:6854
Change-Id: Ia1664bd56f502a81eaa4b2f0e35722b2ff5bea3b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3605765
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>

infra/specs/angle.json

@@ -516,7 +516,7 @@
             }
           ],
           "service_account": "chromium-tester@chops-service-accounts.iam.gserviceaccount.com",
-          "shards": 20
+          "shards": 6
         },
         "test_id_prefix": "ninja://src/tests:angle_perftests/"
       },

infra/specs/test_suites.pyl

@@ -711,7 +711,7 @@
           'shards': 2,
         },
         'android_swarming': {
-          'shards': 20,
+          'shards': 6,
         },
       },
     },

scripts/code_generation_hashes/Test_spec_JSON.json

@@ -1,6 +1,6 @@
 {
   "infra/specs/angle.json":
-    "a0c670a8a4333030406d3774a2f932ca",
+    "6dae94987c7706051871961619e0b230",
   "infra/specs/generate_test_spec_json.py":
     "be4569626aa91f8872664e2d9cef4ac2",
   "infra/specs/mixins.pyl":
@@ -8,7 +8,7 @@
   "infra/specs/test_suite_exceptions.pyl":
     "723460da84a90884a9668c07a0893390",
   "infra/specs/test_suites.pyl":
-    "2cda0c8dbf60699a598ea5217e567354",
+    "7c6c01485c8bf9c98194da6e520c31c5",
   "infra/specs/variants.pyl":
     "8cfcaa99fa07ad2a2d5d14f220fd5037",
   "infra/specs/waterfalls.pyl":