Remove obsolete PropertySourcesPlaceholderConfigurer bean

An PropertySourcesPlaceholderConfigurer bean was still set up which tried to load the legacy properties files.

Refs !137 (merged).

src/main/java/de/thm/arsnova/config/SecurityConfig.java

@@ -289,19 +289,6 @@ public class SecurityConfig extends WebSecurityConfigurerAdapter {
 		logger.info("Enabled authentication providers: {}", providers);
 	}
 
-	@Bean
-	public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
-		final PropertySourcesPlaceholderConfigurer configurer = new PropertySourcesPlaceholderConfigurer();
-		configurer.setLocations(
-				new ClassPathResource("arsnova.properties.example"),
-				new FileSystemResource("file:///etc/arsnova/arsnova.properties")
-		);
-		configurer.setIgnoreResourceNotFound(true);
-		configurer.setIgnoreUnresolvablePlaceholders(false);
-
-		return configurer;
-	}
-
 	@Bean
 	public SessionRegistry sessionRegistry() {
 		return new SessionRegistryImpl();