Switch sed(1) to toybox.

Test: treehugger
Change-Id: I575ae9db8d94cbec811d0029691df98373f8fe35
diff --git a/ui/build/paths/config.go b/ui/build/paths/config.go
index 6ef7fe9..d4922f3 100644
--- a/ui/build/paths/config.go
+++ b/ui/build/paths/config.go
@@ -101,7 +101,6 @@
 	"python3":   Allowed,
 	"realpath":  Allowed,
 	"rsync":     Allowed,
-	"sed":       Allowed,
 	"sh":        Allowed,
 	"tar":       Allowed,
 	"timeout":   Allowed,
@@ -157,6 +156,7 @@
 	"readlink":  LinuxOnlyPrebuilt,
 	"rm":        LinuxOnlyPrebuilt,
 	"rmdir":     LinuxOnlyPrebuilt,
+	"sed":       LinuxOnlyPrebuilt,
 	"setsid":    LinuxOnlyPrebuilt,
 	"sha1sum":   LinuxOnlyPrebuilt,
 	"sha256sum": LinuxOnlyPrebuilt,