Fix typo in documents

I scanned all files in the doc folder with a spell checker (https://github.com/EWSoftware/VSSpellChecker

).
This patch (hopefully) corrected all spell errors that it found.

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/4065)