remove remaining dead code left over from /dev endpoints

db::ensure_dev_athlete was never called (main.rs had its own,
inferior copy, removed in the previous commit). Config::dev_sync_days
and Config::require_api_key were only used by the now-removed
/dev/sync handlers.

src/db.rs

@@ -158,40 +158,6 @@ pub async fn delete_old_oauth_states(db: &PgPool) -> Result<()> {
     Ok(())
 }
 
-pub async fn ensure_dev_athlete(
-    db: &PgPool,
-    intervals_athlete_id: &str,
-    display_name: &str,
-    api_key: &str,
-) -> Result<i64> {
-    let row = sqlx::query(
-        r#"
-        INSERT INTO athletes (
-            intervals_athlete_id,
-            display_name,
-            access_token,
-            scopes
-        )
-        VALUES ($1, $2, $3, 'dev')
-        ON CONFLICT (intervals_athlete_id)
-        DO UPDATE SET
-            display_name = EXCLUDED.display_name,
-            access_token = EXCLUDED.access_token,
-            updated_at = now()
-        RETURNING id
-        "#,
-    )
-    .bind(intervals_athlete_id)
-    .bind(display_name)
-    .bind(api_key)
-    .fetch_one(db)
-    .await?;
-
-    use sqlx::Row;
-
-    Ok(row.try_get("id")?)
-}
-
 /// Create or update an athlete authenticated with a personal API key.
 pub async fn upsert_api_key_athlete(
     db: &PgPool,