fix links with uppercase letters in scheme not being opened

closes #801

app/src/main/java/com/keylesspalace/tusky/util/LinkHelper.java

@@ -126,7 +126,7 @@ public class LinkHelper {
      * @param context context
      */
     public static void openLink(String url, Context context) {
-        Uri uri = Uri.parse(url);
+        Uri uri = Uri.parse(url).normalizeScheme();
 
         boolean useCustomTabs = PreferenceManager.getDefaultSharedPreferences(context)
                 .getBoolean("customTabs", false);