[os-nginx] Disable http2 for a domain

[rdhia]

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Is your feature request related to a problem? Please describe.
there is an issue with Safari browser on some sites when http2 is enabled
1- first request is got in HTTP/2
2- nginx forward it to upstream in HTTP/1.1 (or 1.0) 2 is not possible
3- safari get the first html page but don't proceed with subsequent requests for included resources (css, js..) (may be waiting them to be streamed in http/2 connection)
4- connection fails

the same problem is described also in the forum

Describe the solution you'd like
a checkbox to disable http2 on 'HTTP server' page ui/nginx#subtab_nginx-http-httpserver gui page

Describe alternatives you've considered
adding type='text/css' like in <link rel="stylesheet" type='text/css' href="vendors/bootstrap/dist/css/bootstrap.min.css">
pushed safari to load the resources !

Additional context
os-nginx 1.34
opnsense 24.7.1
http2 always on in /usr/local/opnsense/service/templates/OPNsense/Nginx/http.conf