[LXC] fedora33 EOL [1], upgrade to fedora35 [2]

[1] https://docs.fedoraproject.org/en-US/releases/eol/
[2] https://docs.fedoraproject.org/en-US/releases/f35/

Tested by::

    # build the container ..
    $ sudo -H ./utils/lxc.sh build searx-fedora35

    # open a shell in the container
    $ sudo -H ./utils/lxc.sh cmd searx-fedora35 bash
    [root@searx-fedora35 SearXNG]#

    # install a complete SearXNG suite ..
    [root@searx-fedora35 SearXNG]# ./utils/searx.sh install all
    ...

    # install apache to export the SearXNG instance by HTTP
    [root@searx-fedora35 SearXNG]# ./utils/searx.sh apache install
    ...
    INFO:  got 200 from http://10.174.184.94/searx



To build wheel `python3-devel` needs to be added to SEARX_PACKAGES_fedora::

    |searx|   × Building wheel for setproctitle (pyproject.toml) did not run successfully.
    |searx|   │ exit code: 1
    ...
    |searx|       In file included from src/spt.h:15,
    |searx|                        from src/setproctitle.c:14:
    |searx|       src/spt_python.h:16:10: fatal error: Python.h: No such file or directory
    |searx|          16 | #include <Python.h>
    |searx|             |          ^~~~~~~~~~
    |searx|       compilation terminated.
    |searx|       error: command '/usr/bin/gcc' failed with exit code 1
    |searx|       [end of output]
    ...
    |searx|   ERROR: Failed building wheel for setproctitle

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>