Fix: WebP missing from QMovie::supportedFormats()

Use QImageReader::supportsOption() instead of ::supportsAnimation(),
since the former checks what the handler supports in general, not just
the particular device.

Task-number: QTBUG-61642
Change-Id: I57db24425b4fd8821446659936e6a8ca55008921
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>

src/gui/image/qmovie.cpp

@@ -975,7 +975,7 @@ QList<QByteArray> QMovie::supportedFormats()
 
     const auto doesntSupportAnimation =
             [&buffer](const QByteArray &format) {
-                return !QImageReader(&buffer, format).supportsAnimation();
+                return !QImageReader(&buffer, format).supportsOption(QImageIOHandler::Animation);
             };
 
     list.erase(std::remove_if(list.begin(), list.end(), doesntSupportAnimation), list.end());