[Smalltalk/en] Fix required

> c) wrt Blocks section -Squeak does allow block local vars and certainly allows more than three block arguments. I'm not at all sure why the claim about long term storage and non-local returns is there.
d) Method calls: - that really ought to be refer to Message sends. We don't call methods.

_Originally posted by @divayprakash in https://github.com/adambard/learnxinyminutes-docs/issues/2622#issuecomment-433644977_

Start with the Smalltalk/en documentation and locate the Blocks section and the text about method calls. Review the claims about block-local variables, block arguments, long-term storage, non-local returns, and message sends against the issue details and Squeak terminology. Done means the documentation no longer makes the disputed claims and refers accurately to message sends.

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