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.

- Sean