[meta.endian] Simplify wording, avoid "shall"

Author: tkoeppe

source/utilities.tex

@@ -17130,13 +17130,13 @@
 \pnum
 If all scalar types have size \tcode{1}, then all of \tcode{endian::little},
 \tcode{endian::big}, and \tcode{endian::native} have the same value.
-Otherwise \tcode{endian::little} shall not be equal to \tcode{endian::big}.
-If all scalar types are big-endian, \tcode{endian::native} shall be
+Otherwise, \tcode{endian::little} is not equal to \tcode{endian::big}.
+If all scalar types are big-endian, \tcode{endian::native} is
 equal to \tcode{endian::big}.
-If all scalar types are little-endian, \tcode{endian::native} shall be
+If all scalar types are little-endian, \tcode{endian::native} is
 equal to \tcode{endian::little}.
-Otherwise \tcode{endian::native} shall have a value that is not equal
-to either of \tcode{endian::big} or \tcode{endian::little}.
+Otherwise, \tcode{endian::native} is not equal
+to either \tcode{endian::big} or \tcode{endian::little}.
 \end{itemdescr}
 
 \rSec1[ratio]{Compile-time rational arithmetic}