lts-release-mail: Fix URL for "production" "sandbox RTD"

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I90c2a26c8cba61149de19b79335a7abaa1cb4ff4
diff --git a/lts/lts-release-mail.py b/lts/lts-release-mail.py
index f6fd0e1..13ee2ff 100755
--- a/lts/lts-release-mail.py
+++ b/lts/lts-release-mail.py
@@ -109,7 +109,7 @@
     references = references.rstrip()
 
     if is_sandbox_run():
-        rtd_url = "https://pfalcon-trustedfirmware-a-sandbox.readthedocs.io/en/"
+        rtd_url = "https://trustedfirmware-a-sandbox.readthedocs.io/en/"
     else:
         rtd_url = "https://trustedfirmware-a.readthedocs.io/en/"
     rtd_slug = args.release_tag.lower().replace("/", "-")