MFH: r551605

devel/ipython5: Use newest version of pygments

The pinned dependency 'pygments<2.6' is only necessary to solve an issue with
Python 2.7, and devel/ipython5 is now python3.5+ only. [1] [2]

This fixes a conflict introduced on ports r549076 and r549418 between
textproc/py-pygments and textproc/py-pygments-25 when building at least
textproc/py-sphinx and math/sage.

1 - https://github.com/ipython/ipython/pull/12174
2 - https://github.com/ipython/ipython/issues/12173

PR: 249131, 250074, 250144
Reported by: thierry, swills
Approved by: python (with hat)

Approved by: ports-secteam (fluffy)