[thread.{,j}thread.constr] Turn notes about effects of attributes into notes.

Author: tkoeppe

source/threads.tex

@@ -1857,8 +1857,10 @@
 \end{note}
 If the invocation of \tcode{invoke} terminates with an uncaught exception,
 \tcode{terminate} is invoked\iref{except.terminate}.
+\begin{note}
 The parameters \tcode{attrs...}
 can affect the behavior of the new thread\iref{thread.attributes}.
+\end{note}
 
 \pnum
 \sync
@@ -2238,11 +2240,10 @@
 \end{note}
 If the \tcode{invoke} expression exits via an exception,
 \tcode{terminate} is called.
+\begin{note}
 The parameters \tcode{attrs...}
-%FIXME: why do we have iref{thread.attributes} for thread for the same wording,
-%but not for jthread?
-%While we're at it, could this not be a note?
-can affect the behavior of the new thread.
+can affect the behavior of the new thread\iref{thread.attributes}.
+\end{note}
 
 \pnum
 \sync