remove unused milestone-maintainers OWNERS_ALIASES entry

The k/k top level OWNERS_ALIASES entry for milestone-maintainers
is unused.  Currently everything around milestone maintanence
continues to happen via the kubernetes-milestone-maintainers GitHub
group (see: https://github.com/kubernetes/sig-release/issues/241 for
similar cleaning up effort there).  The hope is in the future this will
move to in repo yaml and Peribolos, but in the meantime this duplicated
and unused list only adds to confusion.

Signed-off-by: Tim Pepper <tpepper@vmware.com>

OWNERS_ALIASES

@@ -242,81 +242,6 @@ aliases:
     - DirectXMan12
     - MaciekPytel
     - mwielgus
-  milestone-maintainers:
-    - lavalamp
-    - deads2k
-    - michelleN
-    - mattfarina
-    - prydonius
-    - bgrant0607
-    - jdumars
-    - liggitt
-    - deads2k
-    - mwielgus
-    - directxman12
-    - justinsb
-    - kris-nova
-    - chrislovecnm
-    - mfburnett
-    - slack
-    - colemickens
-    - foxish
-    - AdoHe
-    - lukemarsden
-    - jbeda
-    - roberthbailey
-    - zehicle
-    - jdumars
-    - grodrigues3
-    - Phillels
-    - devin-donnelly
-    - jaredbhatti
-    - csbell
-    - quinton-hoole
-    - piosz
-    - fabxc
-    - thockin
-    - dcbw
-    - caseydavenport
-    - dchen1107
-    - derekwaynecarr
-    - zen
-    - marcoceppi
-    - dghubble
-    - idvoretskyi
-    - xsgordon
-    - apsinha
-    - idvoretskyi
-    - calebamiles
-    - calebamiles
-    - wojtek-t
-    - countspongebob
-    - jbeda
-    - davidopp
-    - timothysc
-    - pmorie
-    - arschles
-    - vaikas-google
-    - duglin
-    - saad-ali
-    - childsb
-    - spiffxp
-    - fejta
-    - timothysc
-    - danielromlein
-    - floreks
-    - michmike
-    - abgworrall
-    - krzyzacy
-    - steveperry-53
-    - radhikpac
-    - jpbetz
-    - cmluciano
-    - bsalamat
-    - m1093782566
-    - tallclair
-    - feiskyer
-    - mikedanese
   api-approvers:
     - erictune
     - lavalamp