Fix Ruby documentation example errors

Incorporates upstream PR asg017#215 with additional fix:
- Fix extra closing bracket (PR asg017#215)
- Fix incorrect variable name: `query` → `embedding`

Co-Authored-By: Nicolas Buduroi <[email protected]>
Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: 3 people

site/using/ruby.md

@@ -35,6 +35,6 @@ If your embeddings are provided as a list of numbers, use `.pack("f*")` to conve
 
 ```ruby
 embedding = [0.1, 0.2, 0.3, 0.4]
-result = db.execute("SELECT vec_length(?)", [query.pack("f*")]])
+result = db.execute("SELECT vec_length(?)", [embedding.pack("f*")])
 puts result.first.first # 4
 ```