all: delete old Unicode tables

git rm `{git grep -l -E '!go1.(9|1|2[0123])' | grep -v internal/gen}

The go.mod for this repo requires Go 1.24, so remove the code
that is only here for older versions.

Change-Id: I29b5fbc697b34139adc2fb3d8752dbaddfdb3480
Reviewed-on: https://go-review.googlesource.com/c/text/+/738580
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Russ Cox <rsc@golang.org>

Author: rsc