[range.access.general] Use consistent "In addition to being available ..." form

Elsewhere we say "the header" or "any of the headers", e.g. [meta.trans.other],
[tuple.helper], etc.

Author: jwakely

source/ranges.tex

@@ -600,7 +600,7 @@
 \pnum
 In addition to being available via inclusion of the \libheader{ranges}
 header, the customization point objects in \ref{range.access} are
-available when \libheaderrefx{iterator}{iterator.synopsis} is included.
+available when the header \libheaderrefx{iterator}{iterator.synopsis} is included.
 
 \pnum
 Within \ref{range.access},