remove old note

docs.html

@@ -5347,7 +5347,6 @@ to modify the non-zero elements in a safer manner,
 use <a href="#transform">.transform()</a> or <a href="#for_each">.for_each()</a> instead of iterators;
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 writing a zero value into a sparse matrix through an iterator will invalidate all current iterators associated with the sparse matrix</li>
-<li>row iterators for sparse matrices are only useful with Armadillo 8.500 and later versions; in earlier versions they are inefficient
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