Fix typo in noConflict section

reference.html

@@ -5725,7 +5725,7 @@ map.addControl(new MyControl());
 
 <h2 id="noconflict">L.noConflict()</h2>
 
-<p>This method restores the L global variale to the original value it had before Leaflet inclusion, and returns the real Leaflet namespace so you can put it elsewhere, like this:<p>
+<p>This method restores the L global variable to the original value it had before Leaflet inclusion, and returns the real Leaflet namespace so you can put it elsewhere, like this:<p>
 
 <pre><code>// L points to some other library
 ...