Docs: Fix two broken links, per hydra-link-checker (spider-check job)

Author: Krinkle

docs/_data/projects.yml

@@ -35,7 +35,7 @@ orgs:
         href: https://github.com/discourse/discourse-subscriptions
 
   - name: DocumentCloud
-    href: https://www.documentcloud.org/opensource
+    href: https://www.muckrock.com/news/archives/2016/nov/29/muckrock-goes-open-source/
     sub:
       - name: Underscore.js
         href: https://github.com/jashkenas/underscore

docs/browser.md

@@ -257,7 +257,7 @@ Seeking an element by this ID during an event, or during a different test, may w
 
 Demos:
 * [ColorFactory test page](https://krinkle.github.io/node-colorfactory/test/) ([Source code](https://github.com/Krinkle/node-colorfactory/blob/cd79287c09eb0e7118eb4a45811786c65d0640b7/test/testinit.js#L25-L43))
-* [Fabric.js test page](http://fabricjs.com/test/visual/?coverage) ([Source code](https://github.com/fabricjs/fabric.js/blob/v6.0.0-rc5/test/lib/visualCallbackQunit.js#L41))
+* Fabric.js visual test ([Source code](https://github.com/fabricjs/fabric.js/blob/v6.0.0-rc5/test/lib/visualCallbackQunit.js#L41))
 
 The test ID can be obtained from [QUnit.config.current](./api/config/current.md).