@uppy/provider-views: bring back "loaded X files..." (#5097)

As discussed with lakesare in #5050.
Currently the loadedXFiles i18n key is not in use at all,
don't know where/when it got lost in translation.

packages/@uppy/provider-views/src/Browser.tsx

@@ -195,7 +195,9 @@ function Browser<M extends Meta, B extends Body>(
         if (isLoading) {
           return (
             <div className="uppy-Provider-loading">
-              <span>{i18n('loading')}</span>
+              <span>
+                {typeof isLoading === 'string' ? isLoading : i18n('loading')}
+              </span>
             </div>
           )
         }