chore(deps): upgrade ember packages and remove feature flags

.ember-cli.js

@@ -1,7 +1,5 @@
 'use strict';
 
-process.env.EMBER_VERSION = 'OCTANE';
-
 module.exports = {
   /**
     Ember CLI sends analytics information by default. The data is completely

package.json

@@ -42,7 +42,7 @@
     "@types/qunit": "^2.9.0",
     "@types/rsvp": "^4.0.3",
     "broccoli-asset-rev": "^3.0.0",
-    "ember-cli": "github:ember-cli/ember-cli#0667d37709c7192c60f86e0c8c462334a52fd8d6",
+    "ember-cli": "~3.12.0",
     "ember-cli-dependency-checker": "^3.2.0",
     "ember-cli-htmlbars-inline-precompile": "^2.1.0",
     "ember-cli-inject-live-reload": "^2.0.1",
@@ -56,7 +56,7 @@
     "ember-on-modifier": "^1.0.0",
     "ember-qunit": "^4.5.1",
     "ember-resolver": "^5.2.1",
-    "ember-source": "https://s3.amazonaws.com/builds.emberjs.com/canary/shas/319e3ce16e49e226baf6807042be4fe5ce5c8e01.tgz",
+    "ember-source": "https://s3.amazonaws.com/builds.emberjs.com/canary/shas/ebdb582a8423e1ec263a7a563fe0c5f432f96b54.tgz",
     "ember-source-channel-url": "^2.0.1",
     "ember-template-lint": "^1.5.3",
     "ember-try": "^1.2.1",

tests/dummy/config/environment.js

@@ -7,13 +7,7 @@ module.exports = function(environment) {
     rootURL: '/',
     locationType: 'auto',
     EmberENV: {
-      FEATURES: {
-        EMBER_NATIVE_DECORATOR_SUPPORT: true,
-        EMBER_METAL_TRACKED_PROPERTIES: true,
-        EMBER_GLIMMER_ANGLE_BRACKET_NESTED_LOOKUP: true,
-        EMBER_GLIMMER_ANGLE_BRACKET_BUILT_INS: true,
-        EMBER_GLIMMER_FN_HELPER: true
-      },
+      FEATURES: {},
       EXTEND_PROTOTYPES: {
         // Prevent Ember Data from overriding Date.parse.
         Date: false