Update documentation/manual/detailledTopics/configuration/SettingsLogger.md

Today, I found my application does not add any log entry into `logs/application.log`, while it normally prints logs to stdout. To figure out the reason, I read `SettingLogger` document. The document said:

"If you want to fully customize logback, just define a `conf/application-logger.xml` configuration file. Here is the default configuration file used by Play:"

But I didn't have `conf/application-logger.xml`. After minutes of struggle, I finally found that `conf/logger.xml` also works as a configuration file for logging.

So, now I believe the sentence in the document should be changed:

"If you want to fully customize logback, just define a `conf/application-logger.xml`  or `conf/logger.xml`  configuration file. Here is the default configuration file used by Play:"