Error in XCode 15. Property 'completionBlock' with type '(() -> Void)?' cannot override a property with type '(@Sendable () -> Void)?'

[barabashd]

This library will now build using XCode 15.

Solution:
Remove deprecated completionBlock of add '@sendable'.

"""
@available(*, deprecated, message: "use BlockObserver completions instead")
override open var completionBlock: (@sendable () -> Void)? {
"""