Replace cgi.escape by html.escape

This patch removes the deprecation warning, "cgi.escape is deprecated,
use html.escape instead".

searx/webapp.py

@@ -46,7 +46,7 @@ except:
     from sys import exit
 
     exit(1)
-from cgi import escape
+from html import escape
 from datetime import datetime, timedelta
 from werkzeug.contrib.fixers import ProxyFix
 from flask import (