wasm: disable thread configure option

This removes the need for “-no-feature thread”.

Thread support will be added at later point in time,
see QTBUG-64625.

Change-Id: I4d1dedd527aa83d6033bf108f5f34e759517b954
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

configure.json

@@ -1119,6 +1119,7 @@
             "label": "Thread support",
             "purpose": "Provides QThread and related classes.",
             "section": "Kernel",
+            "condition": "!config.wasm",
             "output": [ "publicFeature" ]
         },
         "future": {