Remove duplicated content in CHANGELOG.md

[maxisam]

• Please check if the PR fulfills these requirements
• The commit message follows our guidelines: https://github.com/angular/angular/blob/master/CONTRIBUTING.md#commit-message-format
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
• What is the current behavior? (You can also link to an open issue here)
• What is the new behavior (if this is a feature change)?
• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
• Other information:

remove duplicated content

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[maxisam]

I signed it!

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