doc: add back mention of visa fees to onboarding doc

Thanks to the incredible support from the community in
openjs-foundation/cross-project-council#1240
we were able to amend the OpenJS Foundation travel fund policy to now
cover visa costs (even in case the visa is denied).

Signed-off-by: Darshan Sen <raisinten@gmail.com>
PR-URL: #57730
Reviewed-By: Jordan Harband <ljharb@gmail.com>
Reviewed-By: Ruy Adorno <ruy@vlt.sh>
Reviewed-By: Jake Yuesong Li <jake.yuesong@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: RaisinTen

onboarding.md

@@ -261,8 +261,9 @@ needs to be pointed out separately during the onboarding.
 * The OpenJS Foundation hosts regular summits for active contributors to the
   Node.js project, where we have face-to-face discussions about our work on the
   project. The Foundation has travel funds to cover [participants' expenses][]
-  including accommodations and transportation if needed. Check out
-  the [summit](https://github.com/nodejs/summit) repository for details.
+  including accommodations, transportation, and visa fees (even in case the visa
+  is denied) if needed. Check out the [summit](https://github.com/nodejs/summit)
+  repository for details.
 * If you are interested in helping to fix coverity reports consider requesting
   access to the projects coverity project as outlined in [static-analysis][].