Remove behind_proxy_server API tests.

[Selutario]

Related issue
wazuh/wazuh#7006

Description

Hey team,

As requested in the issue wazuh/wazuh#7006, the behind_proxy_server (which was not being used since wazuh/wazuh#7015) has been deleted. Therefore, the tests related were removed.

Tests results

/var/ossec/framework/python/bin/python3 -m pytest tests/integration/test_api/test_config/
============================================================================================ test session starts =============================================================================================
platform linux -- Python 3.8.2, pytest-6.2.2, py-1.10.0, pluggy-0.13.1
rootdir: /wazuh-qa/tests/integration, configfile: pytest.ini
plugins: html-3.1.1, testinfra-5.0.0, metadata-1.11.0, cov-2.11.1, tavern-1.13.1
collected 62 items                                                                                                                                                                                           

tests/integration/test_api/test_config/test_DOS_blocking_system/test_DOS_blocking_system.py .ss.                                                                                                       [  6%]
tests/integration/test_api/test_config/test_bruteforce_blocking_system/test_bruteforce_blocking_system.py .ss.                                                                                         [ 12%]
tests/integration/test_api/test_config/test_cache/test_cache.py .ss.                                                                                                                                   [ 19%]
tests/integration/test_api/test_config/test_cors/test_cors.py x.                                                                                                                                       [ 22%]
tests/integration/test_api/test_config/test_drop_privileges/test_drop_privileges.py .ss.                                                                                                               [ 29%]
tests/integration/test_api/test_config/test_experimental_features/test_experimental_features.py .ss.                                                                                                   [ 35%]
tests/integration/test_api/test_config/test_host_port/test_host_port.py .s.ss.s.                                                                                                                       [ 48%]
tests/integration/test_api/test_config/test_https/test_https.py .ss.                                                                                                                                   [ 54%]
tests/integration/test_api/test_config/test_jwt_token_exp_timeout/test_jwt_token_exp_timeout.py .ss.                                                                                                   [ 61%]
tests/integration/test_api/test_config/test_logs/test_logs.py .ss.                                                                                                                                     [ 67%]
tests/integration/test_api/test_config/test_rbac/test_rbac_mode.py .ss.                                                                                                                                [ 74%]
tests/integration/test_api/test_config/test_use_only_authd/test_use_only_authd.py .s.s.s.ss.s.s.s.                                                                                                     [100%]

===================================================================== 31 passed, 30 skipped, 1 xfailed, 28 warnings in 649.97s (0:10:49) =====================================================================

Regards,
Selu.