Simplify WeeklyFeedEntryCount

No need for a `BETWEEN`: we want to filter on entries published in the last
week, no need to express is as "entries published between now and last week",
"entries published after last week" is enough.

internal/storage/feed.go

@@ -178,7 +178,7 @@ func (s *Storage) WeeklyFeedEntryCount(userID, feedID int64) (int, error) {
 		WHERE
 			entries.user_id=$1 AND
 			entries.feed_id=$2 AND
-			entries.published_at BETWEEN (now() - interval '1 week') AND now();
+			entries.published_at >= now() - interval '1 week';
 	`
 
 	var weeklyCount int