Update references to old Github organisation

Replace references to ARMmbed organisation with the new
org, Mbed-TLS, following project migration.

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/scripts/ci.requirements.txt b/scripts/ci.requirements.txt
index 209ae3d..1ad983f 100644
--- a/scripts/ci.requirements.txt
+++ b/scripts/ci.requirements.txt
@@ -8,5 +8,5 @@
 pylint == 2.4.4
 
 # Use the earliest version of mypy that works with our code base.
-# See https://github.com/ARMmbed/mbedtls/pull/3953 .
+# See https://github.com/Mbed-TLS/mbedtls/pull/3953 .
 mypy >= 0.780