KitInformation: Make defaultValue take a const Kit *

There is no reason not to.

Change-Id: I4accb0b690173d93ad6f4c9dd0bce66d8de75faa
Reviewed-by: Niels Weber <niels.weber@theqtcompany.com>

src/plugins/cmakeprojectmanager/cmakekitinformation.cpp

@@ -91,7 +91,7 @@ Core::Id CMakeKitInformation::defaultValue()
     return Core::Id();
 }
 
-QVariant CMakeKitInformation::defaultValue(Kit *) const
+QVariant CMakeKitInformation::defaultValue(const Kit *) const
 {
     return defaultValue().toSetting();
 }