Fix typo.

lib/pages/help.dart

@@ -45,7 +45,7 @@ class HelpPage extends StatelessWidget {
                     " adding receipts.",
                   ),
                   Text(
-                    "\n\t\t Tracked items can be swiped left to right for ,"
+                    "\n\t\t Tracked items can be swiped left to right for"
                     " Deletion or right to left for Editing. Items are sorted"
                     " from highest to lowest so that the biggest impacts are"
                     " always in view.",