Bug 1512487 - Pre: Remove unused android-api-16-gradle mozconfig. r=agi

This was Gradle-only and then !Gradle-only.  Now Gradle is required
and this is unused.

Differential Revision: https://phabricator.services.mozilla.com/D31381

--HG--
extra : moz-landing-system : lando

mobile/android/config/mozconfigs/android-api-16-gradle/nightly

@@ -1,7 +0,0 @@
-. "$topsrcdir/mobile/android/config/mozconfigs/common"
-
-. "$topsrcdir/mobile/android/config/mozconfigs/android-api-16/nightly"
-
-ac_add_options --without-gradle
-
-. "$topsrcdir/mobile/android/config/mozconfigs/common.override"

mobile/android/config/mozconfigs/android-api-16-gradle/nightly-artifact

@@ -1,12 +0,0 @@
-. "$topsrcdir/build/mozconfig.artifact.automation"
-
-NO_CACHE=1
-NO_NDK=1
-
-. "$topsrcdir/mobile/android/config/mozconfigs/common"
-
-. "$topsrcdir/mobile/android/config/mozconfigs/android-api-16-gradle/nightly"
-
-. "$topsrcdir/build/mozconfig.artifact"
-
-. "$topsrcdir/mobile/android/config/mozconfigs/common.override"

taskcluster/taskgraph/transforms/tests.py

@@ -765,7 +765,6 @@ def set_treeherder_machine_platform(config, tests):
         'android-api-16/opt': 'android-em-4-3-armv7-api16/opt',
         'android-api-16-pgo/opt': 'android-em-4-3-armv7-api16/pgo',
         'android-x86/opt': 'android-em-4-2-x86/opt',
-        'android-api-16-gradle/opt': 'android-api-16-gradle/opt',
     }
     for test in tests:
         # For most desktop platforms, the above table is not used for "regular"