Only do preloading of assets in production mode.

config/packages/prod/webpack_encore.yaml

@@ -1,4 +1,7 @@
-#webpack_encore:
+webpack_encore:
     # Cache the entrypoints.json (rebuild Symfony's cache when entrypoints.json changes)
     # Available in version 1.2
-    #cache: true
+    cache: true
+
+    # Preload in production
+    preload: false

config/packages/webpack_encore.yaml

@@ -8,7 +8,7 @@ webpack_encore:
     # crossorigin: 'anonymous'
 
     # preload all rendered script and link tags automatically via the http2 Link header
-    preload: true
+    #preload: false
 
     # Throw an exception if the entrypoints.json file is missing or an entry is missing from the data
     # strict_mode: false