Deduplicate changelog

[mneverov]

Signed-off-by: Max Neverov [email protected]

• I added CHANGELOG entry for this change.
• Change is not relevant to the end user.

Changes

Deduplicate changelog. Fixes: #2856

Verification

I used the following command to find duplicates:

awk '/\[.?[0-9]+\]/ {print $2}' CHANGELOG.md | sort | uniq -d

[#1362](https://github.com/thanos-io/thanos/pull/1362)
[#1770](https://github.com/thanos-io/thanos/pull/1770)
[#1838](https://github.com/thanos-io/thanos/pull/1838)
[#2166](https://github.com/thanos-io/thanos/pull/2166)
[#2526](https://github.com/thanos-io/thanos/pull/2526)
[2603](https://github.com/thanos-io/thanos/pull/2603)
[#2667](https://github.com/thanos-io/thanos/pull/2667)
[#2671](https://github.com/thanos-io/thanos/pull/2671)
[#2705](https://github.com/thanos-io/thanos/pull/2705)

Most of these PRs are mentioned both in Added and Changed, except 2166, 2603, 2705

[kakkoyun]

Thanks for contribution. LGTM.

[bwplotka]

It would awesome to make script for this to validate for duplicates.. Or TBH just some tooling for changelog really overall 🤔

[bwplotka]

Something like this: #2999