Update Kotlin and Dokka to 1.6.0

[heubeck]

Bundles #753 and #765

[jponge]

@heubeck I think this works better with #769 in. It'd be great if you could test locally (when you have time)

[heubeck]

@heubeck I think this works better with #769 in. It'd be great if you could test locally (when you have time)

Happy to do so @jponge

[heubeck]

@jponge we need to move the Kotlin baseline to 1.4

[codecov]

Codecov Report

Merging #772 (7365b40) into main (131cc0e) will increase coverage by 0.41%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main     #772      +/-   ##
============================================
+ Coverage     89.85%   90.27%   +0.41%     
- Complexity     3003     3017      +14     
============================================
  Files           377      377              
  Lines         11883    11883              
  Branches       1497     1499       +2     
============================================
+ Hits          10678    10727      +49     
+ Misses          620      585      -35     
+ Partials        585      571      -14     

Impacted Files	Coverage Δ
.../io/smallrye/mutiny/helpers/queues/DrainUtils.java	82.22% <0.00%> (ø)
...mallrye/mutiny/operators/multi/MultiFlatMapOp.java	86.76% <0.00%> (+0.92%)	⬆️
...lrye/mutiny/subscription/SerializedSubscriber.java	88.67% <0.00%> (+0.94%)	⬆️
...allrye/mutiny/operators/uni/UniAndCombination.java	89.53% <0.00%> (+1.16%)	⬆️
...erators/multi/builders/BufferItemMultiEmitter.java	92.10% <0.00%> (+1.31%)	⬆️
...y/operators/multi/builders/IterableBasedMulti.java	84.04% <0.00%> (+2.12%)	⬆️
...subscription/SwitchableSubscriptionSubscriber.java	97.54% <0.00%> (+2.45%)	⬆️
...java/io/smallrye/mutiny/helpers/Subscriptions.java	81.76% <0.00%> (+2.76%)	⬆️
...mallrye/mutiny/operators/multi/FlatMapManager.java	98.61% <0.00%> (+2.77%)	⬆️
...operators/multi/builders/CollectionBasedMulti.java	96.77% <0.00%> (+3.22%)	⬆️
... and 4 more