[mod] remove option ui.static_use_hash (cache busting) (#5004)

Cache busting has caused serious problems for users in the past, here are two
examples:

- https://github.com/searxng/searxng/issues/4419
- https://github.com/searxng/searxng/issues/4481

And it makes development and deployment significantly more complex because it
binds the client side to the server side:

- https://github.com/searxng/searxng/pull/4466

In the light of a decoupled development of the WEB clients from the server side:

- https://github.com/searxng/searxng/pull/4988

is it appropriate to abandon this feature. In fact,  it has been ineffective
since #4436 anyway.

However, the benefit has always been questionable, since at best only a few kB
of data are saved (at least in the context of an image_proxy, the effect is below
the detection limit). Ultimately, the client is responsible for caching.

Related: https://github.com/searxng/searxng/issues?q=label%3A%22clear%20browser%20cache%22

Closes: https://github.com/searxng/searxng/pull/4466
Closes: https://github.com/searxng/searxng/issues/1326
Closes: https://github.com/searxng/searxng/issues/964

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

utils/templates/etc/nginx/default.apps-available/searxng.conf

@@ -19,10 +19,7 @@ location ${SEARXNG_URL_PATH} {
 
 }
 
-# uWSGI serves the static files and in settings.yml we use::
-#
-#   ui:
-#     static_use_hash: true
+# To serve the static files via the HTTP server
 #
 # location ${SEARXNG_URL_PATH}/static/ {
 #     alias ${SEARXNG_STATIC}/;

utils/templates/etc/nginx/default.apps-available/searxng.conf:socket

@@ -16,10 +16,7 @@ location ${SEARXNG_URL_PATH} {
     uwsgi_param    HTTP_X_FORWARDED_FOR  \$proxy_add_x_forwarded_for;
 }
 
-# uWSGI serves the static files and in settings.yml we use::
-#
-#   ui:
-#     static_use_hash: true
+# To serve the static files via the HTTP server
 #
 # location ${SEARXNG_URL_PATH}/static/ {
 #     alias ${SEARXNG_STATIC}/;