Specify that time interval units are seconds (#1311)

conf/app.ini

@@ -306,9 +306,9 @@ COOKIE_NAME = i_like_gitea
 COOKIE_SECURE = false
 ; Enable set cookie, default is true
 ENABLE_SET_COOKIE = true
-; Session GC time interval, default is 86400
+; Session GC time interval in seconds, default is 86400 (1 day)
 GC_INTERVAL_TIME = 86400
-; Session life time, default is 86400
+; Session life time in seconds, default is 86400 (1 day)
 SESSION_LIFE_TIME = 86400
 
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