CHANGELOGs: don't include unreleased changed

Prior to this commit all CHANGELOG.md files contained an `### unreleased`
section list all pending changes in changie fragments. The idea at the time was
to make it easy to understand what changes would be present in an upcoming
release.

In practice these sections were never referred to as most developers would rely
on `git log`. Worse yet they were the primary cause of backports requiring
manual intervention.

As the number of release branches has grown, so has the frequency of
backporting and the frustration of needing to manually re-run `task generate`.

This commit removes the unreleased section with the primary goal of reducing
the toil of backporting commits.

(cherry picked from commit 1d28958)

# Conflicts:
#	charts/redpanda/CHANGELOG.md
#	gotohelm/CHANGELOG.md
#	operator/CHANGELOG.md

Author: chrisseto

Taskfile.yml

@@ -132,7 +132,7 @@ tasks:
     - ./.changes/**/*.md
     - ./.changes/**/*.yaml
     cmds:
-    - changie merge -u '## Unreleased' # Ensure CHANGELOG.mds are up to date.
+    - changie merge # Ensure CHANGELOG.mds are up to date.
 
   build:
     cmds:

charts/redpanda/CHANGELOG.md

@@ -5,12 +5,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and is generated by [Changie](https://github.com/miniscruff/changie).
 
 
-## Unreleased
-### Removed
-* The unrespected`kafkaEndpoint` listener parameter has been removed from `values.yaml`
-### Fixed
-* `authentication_method` is no longer set on `http_api` as redpanda itself does not support authentication on the http API.
-
 ## v5.10.2 - 2025-05-01
 ### Changed
 * `serviceAccount.create` now defaults to `true`.