infra: Remove all references to the OSX 10.10 SDK.

scripts/slave/recipes/chromium_trybot.expected/full_tryserver_blink_mac_blink_dbg.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "tryserver.blink",
       "--builder",
       "mac_blink_dbg",
@@ skipping 101 matching lines @@
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
-      "GYP_DEFINES": "clang=1 component=shared_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' mac_sdk_min=10.10 target_arch=x64 test_isolation_mode=prepare use_goma=1"
+      "GYP_DEFINES": "clang=1 component=shared_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' target_arch=x64 test_isolation_mode=prepare use_goma=1"
     },
     "name": "gclient runhooks (with patch)"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]/src/testing/buildbot/chromium.webkit.json",
       "/path/to/tmp/json"
@@ skipping 199 matching lines @@
       "@@@STEP_LINK@layout_test_results@https://storage.googleapis.com/chromium-layout-test-archives/mac_blink_dbg/571/layout-test-results/results.html@@@",
       "@@@STEP_LINK@(zip)@https://storage.googleapis.com/chromium-layout-test-archives/mac_blink_dbg/571/layout-test-results.zip@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]