Move head(1) to toybox.

Test: clean build
Change-Id: I264c320b4a63e9b0f440791dc20ff99ec910036a
diff --git a/ui/build/paths/config.go b/ui/build/paths/config.go
index 623b3c9..bd810f2 100644
--- a/ui/build/paths/config.go
+++ b/ui/build/paths/config.go
@@ -95,7 +95,6 @@
 	"git":       Allowed,
 	"grep":      Allowed,
 	"gzip":      Allowed,
-	"head":      Allowed,
 	"hexdump":   Allowed,
 	"hostname":  Allowed,
 	"jar":       Allowed,
@@ -162,6 +161,7 @@
 	"comm":     Toybox,
 	"dirname":  Toybox,
 	"env":      Toybox,
+	"head":     Toybox,
 	"id":       Toybox,
 	"od":       Toybox,
 	"paste":    Toybox,