Fixed silly NZBGet 9.1 & libpar2 issue

I'm sorry, my update earlier was faulty, as I only tested it on my development machine.

As the commit says, NZBGet 9.1 checks for two patches that they have written for libpar2. I had these on my dev machine, but realised my mistake when I tried to install elsewhere.

I don't know whether I should update the libpar2 formula to include the patches (the project doesn't appear maintained anymore, so no chance of adding them upstream), or whether I should just disable the check.

If disabling the check is the right move, please accept my apologies and this pull request. Otherwise, let me know and I'll add the patches.

Thanks, Sean.