docs: Minor spelling fix.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@2159 44740490-163a-0410-bde0-09ae8108e29a

docs/simplesamlphp-sp.txt

@@ -43,7 +43,7 @@ If you want mulitple Service Providers in the same site and installation, you ca
 		'entityID' => 'https://sp2.example.org/',
 	),
 
-### Enablig a certificate for your Service Provider
+### Enabling a certificate for your Service Provider
 
 Some Identity Providers / Federations may require that your Service Providers holds a certificate. If you enable a certificate for your Service Provider, it may be able to sign requests and response sent to the Identity Provider, as well as receiving encrypted responses.