Update docs for hasSlicing with inifnite range

[pbackus]

The requirement for opSlice on an infinite range to return the result of take or takeExactly was removed in commit c828a08, which was included in Phobos 2.067.0, released in March 2015. However, the documentation was never updated to take this change into account.

This change updates the documentation and adds a unit test for the "new" behavior.

Fixes bugzilla issue 24348.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	24348	normal	Inaccurate documentation for hasSlicing with infinite range

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#8898"