Remove postcode database build step from GitHub Actions

The .pcod file is already committed to the repo, so we only need to build and deploy the web app

Author: robertpitt

.github/workflows/deploy.yml

@@ -23,9 +23,6 @@ jobs:
       - name: Install dependencies
         run: yarn install --frozen-lockfile
 
-      - name: Build postcode database
-        run: yarn build
-
       - name: Build web app
         run: yarn build:web