fix: upgrade npm for OIDC trusted publishing support

npm 10.x (bundled with Node 20) doesn't support OIDC trusted publishing.
Requires npm 11.5.1+.

Author: MuncleUscles

.github/workflows/deploy-snap.yml

@@ -33,6 +33,9 @@ jobs:
           node-version: 20
           registry-url: 'https://registry.npmjs.org'
 
+      - name: Upgrade npm for OIDC trusted publishing
+        run: npm install -g npm@latest
+
       - name: Install dependencies
         run: yarn workspaces focus genlayer-wallet-plugin