Using the same font when editing and viewing the note

Otherwise the transition seems a bit off. Also, we will soon be
combining both the editor and viewer, so it makes sense for them to look
identical.

lib/screens/journal_browsing.dart

@@ -175,7 +175,7 @@ class NoteViewer extends StatelessWidget {
     ThemeData theme = Theme.of(context);
     theme = theme.copyWith(
       textTheme: theme.textTheme.copyWith(
-        body1: theme.textTheme.body1,
+        body1: theme.textTheme.subhead,
       ),
     );