qga/schema: fix documentation for GuestOSInfo

The documentation for kernel-version and kernel-release on Windows was
swapped.

Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

qga/qapi-schema.json

@@ -1173,10 +1173,10 @@
 #
 # @kernel-release:
 #     * POSIX: release field returned by uname(2)
-#     * Windows: version number of the OS
+#     * Windows: build number of the OS
 # @kernel-version:
 #     * POSIX: version field returned by uname(2)
-#     * Windows: build number of the OS
+#     * Windows: version number of the OS
 # @machine:
 #     * POSIX: machine field returned by uname(2)
 #     * Windows: one of x86, x86_64, arm, ia64