Fix typo

Author: hiroyuki-sato

index.html

@@ -104,7 +104,7 @@ <h3>Set up with JRuby</h3>
 
       <p>Finally, install some Ruby gems.</p>
 
-      <pre><code>embulk gem install embulk -v v0.11.0 # Must be the same Embulk version
+      <pre><code>embulk gem install embulk -v 0.11.0 # Must be the same Embulk version
 embulk gem install msgpack
 embulk gem install bundler # if you need Bundler
 embulk gem install liquid  # if you need Liquid</code></pre>