Update ClientCredentialsAuthenticationConfiguration.java

Removed not allowed character from javadoc

java/src/main/java/org/eclipse/ditto/client/configuration/ClientCredentialsAuthenticationConfiguration.java

@@ -181,7 +181,6 @@ public ClientCredentialsAuthenticationConfigurationBuilder clientId(final String
 
         /**
          * Sets the client secret to authenticate.
-         * <p/>
          * The secret will <strong>never</strong> be sent to a Ditto backend but directly to the configured endpoint.
          *
          * @param clientSecret the client secret.