[3.13] gh-133361: move the explanation of dict equal before its use (GH-133424) (#133621)

gh-133361: move the explanation of dict equal before its use (GH-133424)

Also move up the explanation of insertion order preservation.  Both paragraphs seemed out of place down where they were.
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(cherry picked from commit 61ac88c06e0286cfc6465a47552d41b7dd7e083e)

Co-authored-by: Yongzi Li <1538321957@qq.com>
Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>