website-build: README: fix introduction.

Before being merged with the commit
dc6e1f32c1 ("Import website-build to
build the GNU Boot website."), website-build was a separate git
repository.

And so, even after the merge, until the commit
20d122e94a ("website-build: use website
from local git repository."), it still worked in the same way and
still downloaded the website from git.

However since that commit, website-build stopped downloading the
website from git and built it from the current tree instead, but the
instructions were not updated

This was broken by commit 20d122e94a
("website-build: use website from local git repository.")

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>

website-build/README

@@ -2,10 +2,11 @@
 This project enables to easily build and deploy the GNU Boot website
 with very few commands.
 
-If you want to test your own modifications, you either need to use the
+If you want to test your own modifications to the dependency being
-configure options to use external repositories that have your
+used, you either need to use the configure options to use external
-modifications, or you could also modify the build.sh script to use
+repositories that have your modifications, or you could also modify
-different git repositories and/or revisions.
+the build.sh script to use different git repositories and/or
+revisions.
 
 == Local deployments ==
 Here's how to deploy the website in a local webserver: