(pouchdb#7127) Fix docs for db.query()'s options.reduce default

docs/_includes/api/query_database.html

@@ -27,7 +27,7 @@
   * A full CouchDB-style map/reduce view: `{map : ..., reduce: ...}`.
   * A map function by itself (no reduce).
   * The name of a view in an existing design document (e.g. `'mydesigndoc/myview'`, or `'myview'` as a shorthand for `'myview/myview'`).
-* `options.reduce`: Reduce function, or the string name of a built-in function: `'_sum'`, `'_count'`, or `'_stats'`.  Defaults to `false` (no reduce).
+* `options.reduce`: Reduce function, or the string name of a built-in function: `'_sum'`, `'_count'`, or `'_stats'`.  Defaults to `true` when a reduce function is defined, or `false` otherwise.
     * Tip: if you're not using a built-in, [you're probably doing it wrong](http://youtu.be/BKQ9kXKoHS8?t=865s).
     * PouchDB will always call your reduce function with rereduce == false. As for CouchDB, refer to the [CouchDB documentation](http://docs.couchdb.org/en/1.6.1/couchapp/views/intro.html).
 * `options.include_docs`: Include the document in each row in the `doc` field.