Replace Alfrescro repo with official Shibboleth repo

See: https://shibboleth.atlassian.net/wiki/spaces/DEV/pages/1123844333/Use+of+Maven+Central

Author: LEDfan

pom.xml

@@ -60,8 +60,8 @@
 		</repository>
 		<repository>
 			<!-- Currently used only for the opensaml 2.6.6 dependency -->
-			<id>alfresco</id>
-			<url>https://artifacts.alfresco.com/nexus/content/repositories/public/</url>
+			<id>shibboleth</id>
+			<url>https://build.shibboleth.net/nexus/content/repositories/releases/</url>
 		</repository>
 		<repository>
 			<!-- Currently used only for the spring-social-github 1.0.0.M4 dependency -->