fix: update owners file to remove maintainer (#1502)

Remove Ryan per following comment:

cncf/toc#1024 (comment)

OWNERS.md

@@ -3,7 +3,6 @@
 * Eli Polonsky [@iliapolo](https://github.com/iliapolo)
 * Vinayak Kukreja [@vinayak-kukreja](https://github.com/vinayak-kukreja)
 * Sumu Pitchayan [@sumupitchayan](https://github.com/sumupitchayan)
-* Ryan Parker [@ryparker](https://github.com/ryparker)
 * Evgeny Karasik [@evgenyka](https://github.com/evgenyka)
 * Uday Pant [@udaypant](https://github.com/udaypant)
 * Nathan Taber [@tabern](https://github.com/tabern)