[matlab/en] Fix block comment syntax.

The %{ and %} operators must appear alone on the lines that immediately
precede and follow the block of help text. Do not include any other text
on these lines.

Reference:
http://www.mathworks.com/help/matlab/matlab_prog/comments.html

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In fact, I'm new to matlab, so let me know if I missed something.

I spotted this issue when I found the syntax highlight for block comments for matlab was not correct, so either the block comment syntax or the highlight went wrong. And a quick test in matlab tells...