rootlesskit.installer: s/vendor.conf/vendor.mod/

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

hack/dockerfile/install/rootlesskit.installer

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-# When updating, also update rootlesskit commit in vendor.conf accordingly
+# When updating, also update rootlesskit commit in vendor.mod accordingly
 # v1.1.0
 : "${ROOTLESSKIT_VERSION:=6222b477d4c3ce6eea2bcff0586e43c95d1c0bb7}"