unicode: remove script test

The script test requires a manual update on each new
Unicode release, which interupts the automated flow.
The test is removed in favor of one that fits within the
automated scripts.
See https://go-review.googlesource.com/c/text/+/169638.

Updates golang/go#27945

Change-Id: I9c9f1e2a77f7baef17040ea09eec28d7cf55b5e4
Reviewed-on: https://go-review.googlesource.com/c/go/+/169619


Reviewed-by: Russ Cox <rsc@golang.org>