Use the correct update_allows_fetch_and_merge parameter in the rules mapping

[yurii-kysel]

Previously the update parameter was used to set the update_allows_fetch_and_merge value.
Based on the documentation it should be update_allows_fetch_and_merge in case when update is set to true

Resolves #2463

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Before the change?

• When the update parameter is set to true - update_allows_fetch_and_merge also was set to true automatically, even if we have update_allows_fetch_and_merge: false in our rules

After the change?

• When the update parameter is set to true - update_allows_fetch_and_merge would be set based on the rule we defined in update_allows_fetch_and_merge

Pull request checklist

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

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[yurii-kysel]

The tests were not added, as the use-case is only applicable to forked repositories (which is currently not possible to be created using the terraform). In case with the normal repo, the update_allows_fetch_and_merge would always be false in output