conf: clearer doc comments for mirror config options (#6058)

* conf: clearer doc comments for mirror config options

* conf: apply suggestions from code review

Co-Authored-By: ᴜɴᴋɴᴡᴏɴ <u@gogs.io>

* conf: clearer doc comments for mirror config options - added bindata

Co-authored-by: Gogs <gogs@fake.local>
Co-authored-by: ᴜɴᴋɴᴡᴏɴ <u@gogs.io>
Co-authored-by: gkuehn001 <gkuehn@gmail.com>

conf/app.ini

@@ -415,8 +415,8 @@ ENABLED = true
 ; Run cron tasks when Gogs starts.
 RUN_AT_START = false
 
-; Update mirrors
 [cron.update_mirrors]
+; Defines how often the mirror syncer checks if any mirror needs to be synchronized (based on the mirror update interval).
 SCHEDULE = @every 10m
 
 ; Repository health check
@@ -461,7 +461,8 @@ PULL = 300
 GC = 60
 
 [mirror]
-; The default interval in hours for fetching updates.
+; Defines the default interval (in hours) until the next sync for a mirror (after a successful mirror sync).
+; It can be overridden individually for each mirror repository in the settings.
 DEFAULT_INTERVAL = 8
 
 [api]