Mark rule registry as sendable

[SimplyDanny]

The @unchecked should be fine here given that the registry is initialized once at startup.

This silences a warning in Bazel which blocks release builds.

[SwiftLintBot]

	1 Warning
⚠️	If this is a user-facing change, please include a CHANGELOG entry to credit yourself! You can find it at CHANGELOG.md.

	1 Message
📖	Skipping OSSCheck because SwiftLint hasn't changed compared to 'main'

Here's an example of your CHANGELOG entry:

* Mark rule registry as sendable.  
  [SimplyDanny](https://github.com/SimplyDanny)
  [#issue_number](https://github.com/realm/SwiftLint/issues/issue_number)

note: There are two invisible spaces after the entry's text.

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