doc: fixup after rename of primary nodejs branch

Signed-off-by: Michael Dawson <mdawson@devrus.com>

PR-URL: #43453
Reviewed-By: LiviaMedeiros <livia@cirno.name>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

doc/contributing/security-model-strategy.md

@@ -2,7 +2,7 @@
 
 A clear security model, with features like permissions and policy enforcement,
 is a
-[top technical priority](https://github.com/nodejs/node/blob/master/doc/contributing/technical-priorities.md#permissionspoliciessecurity-model)
+[top technical priority](https://github.com/nodejs/node/blob/HEAD/doc/contributing/technical-priorities.md#permissionspoliciessecurity-model)
 of Node.js.
 
 ## High-level approach