chore(deps-dev): bump ember-source from 3.20.4 to 3.21.0 (#4871)

Bumps [ember-source](https://github.com/emberjs/ember.js) from 3.20.4 to 3.21.0.
- [Release notes](https://github.com/emberjs/ember.js/releases)
- [Changelog](https://github.com/emberjs/ember.js/blob/master/CHANGELOG.md)
- [Commits](emberjs/ember.js@v3.20.4...v3.21.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

package.json

@@ -124,7 +124,7 @@
     "ember-router-scroll": "^3.3.3",
     "ember-simple-auth": "^3.0.0",
     "ember-simple-auth-token": "^5.2.0",
-    "ember-source": "~3.20.4",
+    "ember-source": "~3.21.0",
     "ember-table": "^2.2.3",
     "ember-template-lint": "^2.10.0",
     "ember-truth-helpers": "^2.1.0",

yarn.lock

@@ -7400,10 +7400,10 @@ ember-source-channel-url@^2.0.1:
   dependencies:
     got "^8.0.1"
 
-ember-source@~3.20.4:
-  version "3.20.4"
-  resolved "https://registry.yarnpkg.com/ember-source/-/ember-source-3.20.4.tgz#582545ae3b20de5ffd9f8b43c42c94815e592291"
-  integrity sha512-ycWlaq7W63S3Nh7pMRU4oXNirBB9MbNGDN6hUgs3/qc1gjOUVGfGv0p2NPVcKXgqWtbiqrWGqCbp1iTay2MUpA==
+ember-source@~3.21.0:
+  version "3.21.0"
+  resolved "https://registry.yarnpkg.com/ember-source/-/ember-source-3.21.0.tgz#36ff63584438fba3a336529c30c1aeb14caba9e7"
+  integrity sha512-BoNAhEjB4zb3TuJMzUK81ivz7S6IYLO4MRFfEN8x6nxf3hL9HE0D2QdbqlX9j54xkqssPz5iqmR6/LEEbgP9pA==
   dependencies:
     "@babel/helper-module-imports" "^7.8.3"
     "@babel/plugin-transform-block-scoping" "^7.8.3"