Update to ember-cli@3.16 and ember-source@3.16.

Just to get on the LTS train...

Author: Robert Jackson

package.json

@@ -62,7 +62,7 @@
     "broccoli-test-helper": "^2.0.0",
     "chai": "^4.2.0",
     "co": "^4.6.0",
-    "ember-cli": "~3.15.2",
+    "ember-cli": "~3.16.1",
     "ember-cli-app-version": "^3.2.0",
     "ember-cli-babel": "^7.19.0",
     "ember-cli-dependency-checker": "^3.2.0",
@@ -74,7 +74,7 @@
     "ember-maybe-import-regenerator": "^0.1.6",
     "ember-qunit": "^4.6.0",
     "ember-resolver": "^7.0.0",
-    "ember-source": "~3.15.0",
+    "ember-source": "~3.16.6",
     "ember-source-channel-url": "^2.0.1",
     "ember-try": "^1.4.0",
     "eslint": "^6.8.0",