Remove logic which was moved to new rule 'kdoc'.

[paul-dingemans]

Description

Remove logic which was moved to new rule 'kdoc' in #2548.

Relates #2547

Checklist

Before submitting the PR, please check following (checks which are not relevant may be ignored):

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

Documentation is updated. See difference between snapshot and release documentation

• [ ] Snapshot documentation in case documentation is to be released together with a code change
• [ ] 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