docs: update incorrect default value for `DATABASE_MIN_CONNS` in the man page

miniflux.1

@@ -223,7 +223,7 @@ Default is 20\&.
 .B DATABASE_MIN_CONNS
 Minimum number of database connections\&.
 .br
-Default is 20\&.
+Default is 1\&.
 .TP
 .B DATABASE_URL
 Postgresql connection parameters\&.