Fix corewlan configure test

Configure is unable to find header files that are located in
frameworks. Work around that by specifying "include" on "test" level
instead of "headers" on "corewlan" level.

This amends commit 10adbc4f0f.

Change-Id: I0650585eb9a4e881dc2e3733d8db40c6e50cf1f3
Fixes: QTBUG-72964
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

src/network/configure.json

@@ -28,9 +28,9 @@
             "export": "",
             "test": {
                 "lang": "objc++",
+                "include": [ "CoreWLAN/CoreWLAN.h", "CoreWLAN/CWInterface.h" ],
                 "main": "[CWInterface interfaceWithName:@\"en2\"];"
             },
-            "headers": [ "CoreWLAN/CoreWLAN.h", "CoreWLAN/CWInterface.h" ],
             "sources": [
                 "-framework CoreWLAN -framework Foundation"
             ]