Remove duplicate base_unittests from Mac ASan 64 Tests (1)

testing/buildbot/chromium.memory.json

 {
   "Linux ASan LSan Tests (1)": {
     "gtest_tests": [
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "accessibility_unittests"
       },
       {
@@ skipping 339 matching lines @@
   "Mac ASan 64 Tests (1)": {
     "gtest_tests": [
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "base_unittests"
       },
       {
         "swarming": {
-          "can_use_on_swarming_builders": true
-        },
-        "test": "base_unittests"
-      },
-      {
-        "swarming": {
           "can_use_on_swarming_builders": true,
           "shards": 20
         },
         "test": "browser_tests"
       },
       {
         "test": "cacheinvalidation_unittests"
       },
       {
         "swarming": {
@@ skipping 86 matching lines @@
           "can_use_on_swarming_builders": true
         },
         "test": "unit_tests"
       },
       {
         "test": "url_unittests"
       }
     ]
   }
 }