Remove SHA1 utility used in doc Makefile

doc/Makefile

@@ -1,7 +1,6 @@
 # Makefile for LAMMPS documentation
 
 SHELL         = /bin/bash
-SHA1          = $(shell echo ${USER}-${PWD} | python utils/sha1sum.py)
 BUILDDIR      = ${PWD}
 RSTDIR        = $(BUILDDIR)/rst
 VENV          = $(BUILDDIR)/docenv

doc/utils/sha1sum.py

@@ -1,7 +0,0 @@
-#!/bin/env python
-# simple utility which reimplements sha1sum using Python
-import hashlib
-import sys
-s = hashlib.sha1()
-s.update(sys.stdin.read().encode())
-print(s.hexdigest())