SONAR-8340 add documentation of rolling policy applied to 4 log files

sonar-application/src/main/assembly/conf/sonar.properties

@@ -226,6 +226,9 @@
 #   Compute Engine (aka. CE) logs in ce.log
 #   Elasticsearch (aka. ES) logs in es.log
 #
+# All 4 files follow the same rolling policy (see sonar.log.rollingPolicy and sonar.log.maxFiles) but it applies
+# individually (eg. if sonar.log.maxFiles=4, there can be at most 4 of each files, ie. 16 files in total).
+#
 # All 4 files have logs in the same format:
 #           1           2    3           4                       5                                                   6
 # |-----------------| |---| |-|--------------------||------------------------------| |------------------------------------------------------------------------------------------------------------------------------|