Remove remaining fontawesome usage in templates (#15952)

Can not remove the dependency yet because easymde depends on it.

web_src/less/_base.less

@@ -1162,12 +1162,6 @@ footer {
     padding: 0 .5rem;
     max-width: calc(100vw - 1rem) !important;
 
-    .fa {
-      width: 16px;
-      text-align: center;
-      color: var(--color-primary);
-    }
-
     .links > * {
       border-left: 1px solid var(--color-secondary);
       padding-left: 8px;

web_src/less/_user.less

@@ -34,8 +34,7 @@
               border-bottom: 1px solid var(--color-secondary);
             }
 
-            .svg,
-            .fa {
+            .svg {
               margin-left: 1px;
               margin-right: 5px;
             }