FIX: More 404 image requests in test

A few tests were removed that were testing a subforum for the logo,
which I don't think gain us much anymore. We use `getURL` everywhere and
needn't test it so much. Plus, over time it's always good to remove
a few tests here and there :)

test/javascripts/components/image-uploader-test.js

@@ -3,7 +3,7 @@ moduleForComponent("image-uploader", { integration: true });
 
 componentTest("with image", {
   template:
-    "{{image-uploader imageUrl='/some/upload.png' placeholderUrl='/not/used.png'}}",
+    "{{image-uploader imageUrl='/images/avatar.png' placeholderUrl='/not/used.png'}}",
 
   async test(assert) {
     assert.equal(