spelling: existence

Signed-off-by: Josh Soref <2119212+jsoref@users.noreply.github.com>

src/Security/ExAuth.php

@@ -153,7 +153,7 @@ class ExAuth
 			if (is_array($aCommand)) {
 				switch ($aCommand[0]) {
 					case 'isuser':
-						// Check the existance of a given username
+						// Check the existence of a given username
 						$this->isUser($aCommand);
 						break;
 					case 'auth':
@@ -225,7 +225,7 @@ class ExAuth
 	}
 
 	/**
-	 * Check remote user existance via HTTP(S)
+	 * Check remote user existence via HTTP(S)
 	 *
 	 * @param string  $host The hostname
 	 * @param string  $user Username