[thread.lock.algorithm] Use code font for try_lock().

Author: jwakely

source/threads.tex

@@ -2547,7 +2547,7 @@
 first until all arguments have been processed or a call to \tcode{try_lock()} fails,
 either by returning \tcode{false} or by throwing an exception. If a call to
 \tcode{try_lock()} fails, \tcode{unlock()} shall be called for all prior arguments
-and there shall be no further calls to try_lock().
+and there shall be no further calls to \tcode{try_lock()}.
 
 \pnum
 \returns \tcode{-1} if all calls to \tcode{try_lock()} returned \tcode{true},