[release-3.0] fix changelog for rc.1 (#13197)

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#### What this PR does

follow-up of #13193 

this is breaking the build process. this means that the rc.1 binaries
will be built on a different hash compared to the actual git tag. That's
not ideal, but i'll also cut rc.2 today, so this won't be in the final
release

it's claude's fault

#### Which issue(s) this PR fixes or relates to

Fixes #<issue number>

#### Checklist

- [ ] Tests updated.
- [ ] Documentation added.
- [ ] `CHANGELOG.md` updated - the order of entries should be
`[CHANGE]`, `[FEATURE]`, `[ENHANCEMENT]`, `[BUGFIX]`. If changelog entry
is not needed, please add the `changelog-not-needed` label to the PR.
- [ ]
[`about-versioning.md`](https://github.com/grafana/mimir/blob/main/docs/sources/mimir/configure/about-versioning.md)
updated with experimental features.

Signed-off-by: Dimitar Dimitrov <[email protected]>

Author: dimitarvdimitrov

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## main / unreleased
 
-## 3.0.0-rc.1 2025-10-28
+## 3.0.0-rc.1
 
 ### Jsonnet