Revert of Download the hermetic xcode toolchain on all bots that target mac.

scripts/slave/recipes/swarming/staging.expected/mac_Release.json

Index: scripts/slave/recipes/swarming/staging.expected/mac_Release.json
diff --git a/scripts/slave/recipes/swarming/staging.expected/mac_Release.json b/scripts/slave/recipes/swarming/staging.expected/mac_Release.json
index bfbf043315050cc60b2c3341bd3c951a9a4688ea..1596ece11eb72289f5cf8f1af63e81089c6d7250 100644
--- a/scripts/slave/recipes/swarming/staging.expected/mac_Release.json
+++ b/scripts/slave/recipes/swarming/staging.expected/mac_Release.json
@@ -198,7 +198,6 @@
     ],
     "cwd": "[SLAVE_BUILD]/src",
     "env": {
-      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "GYP_DEFINES": "clang=1 component=static_library gomadir='[CACHE]/cipd/goma' target_arch=x64 test_isolation_mode=prepare use_goma=1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
@@ -228,7 +227,6 @@
       "/path/to/tmp/json"
     ],
     "env": {
-      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "clang_revision",
@@ -277,7 +275,6 @@
       "chromium_swarm_tests"
     ],
     "env": {
-      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "compile",