[iterator.concept.sizedsentinel] Avoid potential ambiguity between

inclusive and exclusive "or" by using "and/or".

Author: zygoloid

source/iterators.tex

@@ -1585,7 +1585,7 @@
 Pursuant to \ref{namespace.std},
 users may specialize \tcode{disable_sized_sentinel}
 for cv-unqualified non-array object types \tcode{S} and \tcode{I}
-if either \tcode{S} or \tcode{I} is a program-defined type.
+if \tcode{S} and/or \tcode{I} is a program-defined type.
 Such specializations shall
 be usable in constant expressions\iref{expr.const} and
 have type \tcode{const bool}.