qtdeclarative: enable qml_network

QQmlEngine::networkAccessManager() exists only under QT_CONFIG(qml_network),
a qtdeclarative feature separate from QT_FEATURE_network, which was already ON.
kirigami failed on it:
  src/primitives/icon.cpp:469: 'class QQmlEngine' has no member named
  'networkAccessManager'

qtbase builds libQt6Network here, so enabling the feature restores kirigami's
remote icon loading instead of compiling the capability out.

local/recipes/qt/qtdeclarative/recipe.toml

@@ -254,6 +254,7 @@ cmake "${COOKBOOK_SOURCE}" \
  -DQT_FEATURE_qml_jit=OFF \
  -DQT_FEATURE_ssl=ON \
     -DQT_FEATURE_network=ON \
+    -DQT_FEATURE_qml_network=ON \
     -DQT_FEATURE_localserver=ON \
     -DQT_FEATURE_http=ON \
     -DQT_FEATURE_udpsocket=ON \