Fix inaccuracies in spawn and defer descriptions.

[Sleitnick]

Changes

• Fixes task.defer description that stated that it runs the code on the next resumption cycle. This is false. It runs at the end of the current resumption cycle.
• Fixes task.defer and task.spawn inaccuracy that states they do not return anything. They both return a thread object, which is reflected in the return value section of the documentation. Thus, these sentences are removed.

Checks

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