rely on gpx postinstall script to build the library

.github/workflows/deploy.yml

@@ -18,12 +18,6 @@ jobs:
           cache-dependency-path: |
             gpx/package-lock.json
             website/package-lock.json
-      
-      - name: Install dependencies for gpx
-        run: npm install --prefix gpx
-
-      - name: Build gpx
-        run: npm run build --prefix gpx
 
       - name: Install dependencies for website
         run: npm install --prefix website