[chore] Update codeowners according to releases-approvers RFC (#37806)

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Ex. Adding a feature - Explain what this achieves.-->
#### Description
This PR adds the releases-approvers user group as codeowners for all
files related to the release.

<!-- Issue number if applicable -->
#### Link to tracking issue
Parf of
open-telemetry/opentelemetry-collector#11577



<!--Describe the documentation added.-->
#### Documentation

https://github.com/open-telemetry/opentelemetry-collector/blob/main/docs/rfcs/release-approvers.md

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Signed-off-by: Moritz Wiesinger <moritz.wiesinger@dynatrace.com>

.github/CODEOWNERS

@@ -11,6 +11,11 @@
 
 * @open-telemetry/collector-contrib-approvers
 
+# Files owned by collector-releases-approvers
+.github/workflows/prepare-release.yml                            @open-telemetry/collector-contrib-approvers @open-telemetry/collector-releases-approvers
+.github/workflows/scripts/release-prepare-release.sh             @open-telemetry/collector-contrib-approvers @open-telemetry/collector-releases-approvers
+.github/workflows/scripts/set_release_tag.sh                     @open-telemetry/collector-contrib-approvers @open-telemetry/collector-releases-approvers
+
 # Start components list
 
 cmd/githubgen/                                                   @open-telemetry/collector-contrib-approvers @atoulme