textproc/py-pygments: Remove outdated CONFLICTS_INSTALL

textproc/py-pygments-25 has been removed 8 months ago.

Reference: https://cgit.freebsd.org/ports/commit/?id=3df4e19a61cf19631b3d92322394450a1daa7c10
Approved by: portmgr (blanket)
With hat: python