[SPARK][EXAMPLE] Added missing semicolon in quick-start-guide example

## What changes were proposed in this pull request?

Added missing semicolon in quick-start-guide java example code which wasn't compiling before.

## How was this patch tested?
Locally by running and generating site for docs. You can see the last line contains ";" in the below snapshot.
![image](https://cloud.githubusercontent.com/assets/10628224/20751760/9a7e0402-b723-11e6-9aa8-3b6ca2d92ebf.png)

Author: manishAtGit <manish@knoldus.com>

Closes #16081 from manishatGit/fixed-quick-start-guide.

docs/quick-start.md

@@ -330,7 +330,7 @@ public class SimpleApp {
 
     System.out.println("Lines with a: " + numAs + ", lines with b: " + numBs);
     
-    sc.stop()
+    sc.stop();
   }
 }
 {% endhighlight %}