systemctl: reflect that statically enabled units can be in .upholds/

Follow-up for 38f9017

src/systemctl/systemctl-enable.c

@@ -254,7 +254,7 @@ int verb_enable(int argc, char *argv[], void *userdata) {
                            " \n" /* trick: the space is needed so that the line does not get stripped from output */
                            "Possible reasons for having this kind of units are:\n"
                            "%1$s A unit may be statically enabled by being symlinked from another unit's\n"
-                           "  .wants/ or .requires/ directory.\n"
+                           "  .wants/, .requires/, or .upholds/ directory.\n"
                            "%1$s A unit's purpose may be to act as a helper for some other unit which has\n"
                            "  a requirement dependency on it.\n"
                            "%1$s A unit may be started when needed via activation (socket, path, timer,\n"