py2-pygments: fix shebang for pygmentize

`pygmentize` contains a full path to non-relocated Python. The patch
changes shebang to `#!/usr/bin/env python`.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
Merge pull request #1209 from davidlt/py2-pygments-fix-python-path

py2-pygments: fix shebang for pygmentize