Update OWNERS_ALIASES

Per chat with Celeste, this commit also reflects her offboarding from the reviewers/approvers team.

Author: divya-mohan0209

OWNERS_ALIASES

@@ -54,7 +54,6 @@ aliases:
     - bene2k1
     - rlenferink
   sig-docs-en-owners: # Admins for English content
-    - celestehorgan
     - dipesh-rawat
     - divya-mohan0209
     - katcosgrove
@@ -65,7 +64,6 @@ aliases:
     - sftim
     - tengqm
   sig-docs-en-reviews: # PR reviews for English content
-    - celestehorgan
     - dipesh-rawat
     - divya-mohan0209
     - katcosgrove