[mod] migrate from Redis to Valkey (#4795)

This patch migrates from `redis==5.2.1` [1] to `valkey==6.1.0` [2].

The migration to valkey is necessary because the company behind Redis has decided
to abandon the open source license. After experiencing a drop in user numbers,
they now want to run it under a dual license again. But this move demonstrates
once again how unreliable the company is and how it treats open source
developers.

To review first, read the docs::

    $ make docs.live

Follow the instructions to remove redis:

- http://0.0.0.0:8000/admin/settings/settings_redis.html

Config and install a local valkey DB:

- http://0.0.0.0:8000/admin/settings/settings_valkey.html

[1] https://pypi.org/project/redis/
[2] https://pypi.org/project/valkey/

Co-authored-by: HLFH <gaspard@dhautefeuille.eu>
Co-authored-by: Markus Heiser <markus.heiser@darmarit.de>

docs/src/searx.redisdb.rst

@@ -1,8 +0,0 @@
-.. _redis db:
-
-========
-Redis DB
-========
-
-.. automodule:: searx.redisdb
-  :members:

docs/src/searx.redislib.rst

@@ -1,8 +0,0 @@
-.. _searx.redis:
-
-=============
-Redis Library
-=============
-
-.. automodule:: searx.redislib
-  :members:

docs/src/searx.valkeydb.rst

@@ -0,0 +1,8 @@
+.. _valkey db:
+
+==========
+Valkey DB
+==========
+
+.. automodule:: searx.valkeydb
+  :members:

docs/src/searx.valkeylib.rst

@@ -0,0 +1,8 @@
+.. _searx.valkey:
+
+==============
+Valkey Library
+==============
+
+.. automodule:: searx.valkeylib
+  :members: