Install latest npm (#502)

Signed-off-by: Jens Reinecke <jens.reinecke@arm.com>

Author: jreineckearm

.github/workflows/build-push.yml

@@ -113,6 +113,8 @@ jobs:
         with:
           node-version: '22'
           registry-url: 'https://registry.npmjs.org'
+      - name: Update npm (OIDC/provenance support)
+        run: npm i -g npm@latest
       - name: Build
         run: yarn
       - name: Publish (OIDC)