docs: add Mattia Lavacca as Gateway API maintainer (#3231)

Author: shaneutt

OWNERS_ALIASES

@@ -10,6 +10,7 @@ aliases:
 
   # Reference: https://github.com/kubernetes/org/blob/main/config/kubernetes-sigs/sig-network/teams.yaml
   gateway-api-maintainers:
+    - mlavacca
     - robscott
     - shaneutt
     - youngnick
@@ -32,20 +33,17 @@ aliases:
     - arkodg
     - LiorLieberman
     - michaelbeaumont
-    - mlavacca
     - sunjayBhatia
     - xunzhuo
 
   gateway-api-conformance-approvers:
     - arkodg
-    - mlavacca
     - sunjayBhatia
 
   gateway-api-gep-reviewers:
     - candita
     - gcs278
     - LiorLieberman
-    - mlavacca
 
   gwctl-approvers:
     - gauravkghildiyal