Fix module name typo

Reported by Jens Thiele.
It has been overlooked since r7rs-setup creates a proper module
and populates it.

lib/scheme/time.scm

@@ -1,4 +1,4 @@
 ;;
 ;; This is a cushion module to use R7RS (scheme time) from Gauche
 ;;
-(define-module scheme.timen (use r7rs-setup))
+(define-module scheme.time (use r7rs-setup))