[fix] pip install -e: legacy editable install (setup.py develop) is deprecated

From [1]: There is now a standardized mechanism [2] for an installer like pip to
request an editable install of a project.  pip is transitioning to using this
standard only instead of invoking the deprecated `setup.py develop` command.

For backward compatibility, we can use switches:

--use-pep517
  https://pip.pypa.io/en/stable/cli/pip_install/#cmdoption-use-pep517

--no-build-isolation
  https://pip.pypa.io/en/stable/cli/pip_install/#cmdoption-no-build-isolation

- [1] https://github.com/pypa/pip/issues/11457
- [2] https://peps.python.org/pep-0660/

Closes: https://github.com/searxng/searxng/issues/3701
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

utils/searxng.sh

@@ -501,7 +501,7 @@ pip install -U setuptools
 pip install -U wheel
 pip install -U pyyaml
 cd ${SEARXNG_SRC}
-pip install -e .
+pip install --use-pep517 --no-build-isolation -e .
 EOF
 }
 
@@ -569,7 +569,7 @@ pip install -U pip
 pip install -U setuptools
 pip install -U wheel
 pip install -U pyyaml
-pip install -U -e .
+pip install -U --use-pep517 --no-build-isolation -e .
 EOF
     rst_para "update instance's settings.yml from ${SEARXNG_SETTINGS_PATH}"
     DEFAULT_SELECT=2 \