Update coding standard link and description

The oss-generic link for the coding standard is obsolete. At the same
time, the description vaguely refers to a module.

Let's change the coding standard link to the one used by SE-EDU and
remove the reference to the module.

config/checkstyle/checkstyle.xml

@@ -4,8 +4,8 @@
     "https://checkstyle.org/dtds/configuration_1_3.dtd">
 
 <!--
-    This configuration file enforces rules for a modified version of the module's code standard at
-    https://oss-generic.github.io/process/codingstandards/coding-standards-java.html
+    This configuration file enforces rules for the coding standard at
+    https://se-education.org/guides/conventions/java/intermediate.html
 -->
 
 <module name="Checker">