fix: don't remove arrow from lambdas that are when/if leaf nodes

[tKe]

Description

this fixes a problem with the function-literal rule removing non-redundant arrows from lambdas that are direct leafs of a when-entry or then/else. Without the arrow, the expression is left as a block instead.

Checklist

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• Commit message are well written. In addition to a short title, the commit message also explain why a change is made.
• At least one commit message contains a reference Closes #<xxx> or Fixes #<xxx> (replace<xxx> with issue number)
• Tests are added
• KtLint format has been applied on source code itself and violations are fixed
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• PR description added (background information)

Documentation is updated. See difference between snapshot and release documentation

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• Release documentation in case documentation is related to a released version of ktlint and has to be published as soon as the change is merged to master

[paul-dingemans]

Tnx for your contribution. I refactored the code a bit, so that it complies more with current coding styles.