doc: fix v14.x link maintaining openssl guide

PR-URL: #45071
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/contributing/maintaining-openssl.md

@@ -11,7 +11,7 @@ currently need to generate four PRs as follows:
   of this guide.
 * a PR for 16.x following the instructions in the v16.x-staging version
   of this guide.
-* a PR for 14.x following the instructions in the v14.x-staging version
+* a PR for 14.x following the instructions in the [v14.x-staging version][]
   of this guide.
 
 ## Use of the quictls/openssl fork
@@ -154,3 +154,5 @@ regenerated and committed by:
 ```
 
 Finally, build Node.js and run the tests.
+
+[v14.x-staging version]: https://github.com/nodejs/node/blob/v14.x-staging/doc/guides/maintaining-openssl.md