Move xxd(1) to toybox.

Test: treehugger
Change-Id: I906b0c94da5b65dc387ae253492356ca78f93fd2
diff --git a/ui/build/paths/config.go b/ui/build/paths/config.go
index a81011f..b0d9e72 100644
--- a/ui/build/paths/config.go
+++ b/ui/build/paths/config.go
@@ -144,7 +144,6 @@
 	"wc":        Allowed,
 	"which":     Allowed,
 	"xargs":     Allowed,
-	"xxd":       Allowed,
 	"xz":        Allowed,
 	"zip":       Allowed,
 	"zipinfo":   Allowed,
@@ -178,6 +177,7 @@
 	"uname":  Toybox,
 	"uniq":   Toybox,
 	"whoami": Toybox,
+	"xxd":    Toybox,
 }
 
 func init() {