Adjust patches for qtsvg CVE-2025-10728 and CVE-2025-10729 for Qt 6.7

The first hunk in the patch for CVE-2025-10728 is not needed for Qt 6.7
because the change that is reverted by this hunk exists only in Qt 6.8+.
The changes for the tests do not apply cleanly to Qt 6.7, but we don't
build the tests anyway so that we can omit them.