[std] Remove 'is required' from notes

Author: jensmaurer

source/lex.tex

@@ -665,8 +665,7 @@
 (collectively, ``whitespace''), as described below, are ignored except
 as they serve to separate tokens.
 \begin{note}
-Some whitespace is
-required to separate otherwise adjacent identifiers, keywords, numeric
+Whitespace can separate otherwise adjacent identifiers, keywords, numeric
 literals, and alternative tokens containing alphabetic characters.
 \end{note}
 \indextext{token|)}