Fix incorrect "fork check" condition

Author: flobernd

.github/workflows/validate-pr.yml

@@ -3,6 +3,7 @@ name: Validate APIs
 on:
   pull_request:
     paths:
+      - '**'
       - 'specification/**'
       - '!specification/_types/**'
       - '!specification/_spec_utils/**'
@@ -13,9 +14,16 @@ on:
       - main
 
 jobs:
+  # debug:
+  #   name: debug
+  #   runs-on: ubuntu-latest
+  #   steps:
+  #     - run: |
+  #         echo '${{ toJSON(github.event.pull_request) }}
+
   validate-pr:
     name: build
-    if: github.repository_owner == 'elastic' # this action will fail if executed from a fork
+    if: github.event.pull_request.head.repo.owner.login == 'elastic' # this action will fail if executed from a fork
     runs-on: ubuntu-latest
     env:
       STACK_VERSION: 8.9-SNAPSHOT