Added comment to exception catch

Author: jguittard

src/Selenium2Driver.php

@@ -795,7 +795,7 @@ private function clickOnElement(Element $element)
         } catch (UnknownCommand $e) {
             // If the Webdriver implementation does not support moveto (which is not part of the W3C WebDriver spec), proceed to the click
         } catch (UnknownError $e) {
-            
+            // Chromium driver sends back UnknowError (WebDriver\Exception with code 13)
         }
 
         $element->click();