Dependencies: move dependency on 'packaging' to the extras list for Redis (#2524)

* Depdendencies: move `packaging` to `redis` extras.

The `packaging` dependency is only used by the Redis transport,
so we can omit it from the base/default dependencies of Kombu.

Follow-up / cleanup for pull request #2294.

* Nitpick: restore end-of-file end-of-line to `requirements/default.txt`

Author: jayaddison

requirements/default.txt

@@ -1,4 +1,3 @@
 amqp>=5.3.1,<6.0.0
 vine==5.1.0
 tzdata>=2026.2
-packaging

requirements/extras/redis.txt

@@ -1 +1,2 @@
 redis>=5.3.1,<8.0.0
+packaging