fix: typo (#6528)

Author: k725

.env.template

@@ -348,7 +348,7 @@
 ## Default: 2592000 (30 days)
 # ICON_CACHE_TTL=2592000
 ## Cache time-to-live for icons which weren't available, in seconds (0 is "forever")
-## Default: 2592000 (3 days)
+## Default: 259200 (3 days)
 # ICON_CACHE_NEGTTL=259200
 
 ## Icon download timeout