website: remove unused root path on building website (#3248)

We no longer use the `--root` option of `build_website.py` since we have
moved to jqlang.org (from jqlang.github.io/jq where the root was `/jq`).
We don't need the option on local development either since `http.server`
has the `-d` option to specify the directory to serve from.

docs/build_website.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-import argparse
 import glob
 import itertools
 from jinja2 import Environment, FileSystemLoader, select_autoescape, pass_context
@@ -11,10 +10,6 @@ import re
 import shutil
 import yaml
 
-parser = argparse.ArgumentParser()
-parser.add_argument('--root', default='')
-args = parser.parse_args()
-
 env = Environment(
     loader=FileSystemLoader('templates'),
     autoescape=select_autoescape(['html.j2']),
@@ -27,8 +22,6 @@ def load_yml_file(fn):
 
 
 env.globals['url'] = 'https://jqlang.org'
-env.globals['root'] = args.root
-
 env.filters['search_id'] = lambda input: input.replace(r'`', '')
 env.filters['section_id'] = lambda input: re.sub(
     r'[^-a-zA-Z0-9_]', '', input.replace(' ', '-')).lower()