Put conditioned header under appropriate feature configuration

- Add #if QT_CONFIG(mimetype) for qmimetype.h usage
in removed_api.cpp

Amends 5dbd6a44d8

Change-Id: I0ef3c07bba7c3df56cfd1551d8962ab2efc15651
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Tasuku Suzuki <tasuku.suzuki@signal-slot.co.jp>

src/corelib/compat/removed_api.cpp

@@ -1040,12 +1040,14 @@ bool QJsonValue::operator!=(const QJsonValue &other) const
 
 #include "qline.h" // inlined API
 
+#if QT_CONFIG(mimetype)
 #include "qmimetype.h"
 
 bool QMimeType::operator==(const QMimeType &other) const
 {
     return comparesEqual(*this, other);
 }
+#endif // QT_CONFIG(mimetype)
 
 #include "qobject.h"
 #include "qnumeric.h"