Delete common.scss

Discourse_test/common/common.scss

-.hello-world-banner {
-    height: 300px;
-    width: 100%;
-    background: red;
-    display: flex;
-    align-items: center;
-    justify-content: center;
-    margin-bottom: 1em;
-}
-
-.hello-world {
-    font-size: 8em;
-    color: white;
-}