lang/mono: Remove $FreeBSD$ from patches

Patches aren't supposed to have $FreeBSD$ tags anymore. The
fbsd:nokeywords property was properly set, so the $FreeBSD$ tag was not
even expanded, so these tags were removed. Note that the mini-exceptions
patch is no longer needed. According to the comments, it's is for
FreeBSD 8 support only.

Approved by: portmgr (mat)