fix: log4j appender throwing null pointer exception

[AndresArcones]

In the current implementation of the log4j ScalyrAppender, the getLayout() method will always return null because the layout is not being read. This occurs because the requiresLayout() method is set to return false in ScalyrAppender. As a result, even if a layout is configured for this appender in the logger configuration, it will not be utilized. To fix this issue, the requiresLayout() method should return true, allowing the layout to be read and applied properly.

For reference, see the Appender class in Apache Log4j where requiresLayout() is used to determine if a layout is required.

[AndresArcones]

is there any maintainers on this repository that have the right to merge this pull request? @steve-scalyr @soboko @moriarty-s3a @rvangsgaard @moriarty-s3a @ArthurKamalov