Refine list of QtConcurrent examples to be removed

Review the list of QtConcurrent examples under

https://intranet.qt.io/pages/viewpage.action?pageId=161517211#ExamplesforH1/23bonustarget-QtConcurrent

and review their need using the guideline below:

1. Identify examples with partly overlapping or obsolete features/API usages and remove the inferior one.
2. Provided the API demoed by an example is rather simple but important to show, consider replacing it by converting it to a targeted snippet.
3. Be brave and assess whether we can live without the example despite having an API gap. For example this might be possible if the API is very easy to understand, has very good class descriptions or other extenuating circumstances.

Mark the to-be-removed examples in the above table such that other devs (if not yourself) can do the actual removal in time for the Qt 6.5.0 release. Please also add comment here which examples were tagged for removal.

Definition of done for this task: All examples considered and the to-be-removed ones marked/stated.