doc: add Triagers section to table of contents in GOVERNANCE.md

PR-URL: https://github.com/nodejs/node/pull/34504


Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Harshitha K P <harshitha014@gmail.com>