Fix missing build step in publish workflow (#2734)

The execution environment wasn't built in de publish workflow, resulting
in the execution bundles not being part of the NPM package.

.github/workflows/publish-release.yml

@@ -70,6 +70,7 @@ jobs:
         run: |
           yarn install --immutable
           yarn build
+          yarn workspace @metamask/snaps-execution-environments run build:lavamoat
       - uses: actions/cache@v4
         id: restore-build
         with: