net/freerdp: ffmpeg 6 support - replace url to patch

https://github.com/FreeRDP/FreeRDP/commit/e6d13a25204bae8c1b36f6036d30be6789219312
was added by misstake (isn't attached to any branch) - replaced with
https://github.com/FreeRDP/FreeRDP/commit/61983cd6dcb86097d91b7ef405abc1266444a368
(attached to main).
Code in the commits is same.

Reported by: diizzy (IRC)
Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D40504