luci-app-squid: remove variable redeclaration

Since 22d4830 the form variables m, s, and o was changed to be declared
with let instead of var, but the o variable was redeclared in the app,
resulting in a redeclaration error when it was changed to instead be
declared with let.

Signed-off-by: Daniel Nilsson <dannil+github@protonmail.com>

applications/luci-app-squid/htdocs/luci-static/resources/view/squid.js

@@ -49,7 +49,7 @@ return view.extend({
 		s.tab('general', _('General Settings'));
 		s.tab('advanced', _('Advanced Settings'));
 
-		var o = s.taboption('general', form.Value, 'config_file', _('Config file'));
+		o = s.taboption('general', form.Value, 'config_file', _('Config file'));
 		o.datatype = 'string';
 		o.default = '/etc/squid/squid.conf';
 		o.validate = function(section_id, value) {