[intro.races] Rephrase questionable phrasing in note

Author: jensmaurer

source/basic.tex

@@ -6385,7 +6385,7 @@
 \item $A$ happens before $X$ and $X$ happens before $B$.
 \end{itemize}
 \begin{note}
-An evaluation cannot happen before itself.
+An evaluation does not happen before itself.
 \end{note}
 
 \pnum