Fix default file log level in logging guide

[xstefank]

According to [1] it should be ALL.

[1] https://github.com/quarkusio/quarkus/blob/master/core/runtime/src/main/java/io/quarkus/runtime/logging/FileConfig.java#L43

Not sure if issue is needed. If so, I will create one and update this PR.

[gsmet]

@dmlloyd could you take a look at this one?

Is the default really supposed to be ALL? It doesn't seem right.

[dmlloyd]

The default is ALL because normally the file handler will log everything that is enabled by category (the default for most categories is INFO or WARN). Otherwise, if you enable DEBUG or TRACE for some category, you won't see them output anywhere.

The console OTOH is normally set at INFO because having a flood of output on the console is not normally useful.