fixup markup

Author: jensmaurer

source/threads.tex

@@ -5145,7 +5145,7 @@
 with the value pointed to by \tcode{this} and the first parameter
 as the arguments.
 \item
-For \tcode{fetch_fmaximum}_num and \tcode{fetch_fminimum_num},
+For \tcode{fetch_fmaximum_num} and \tcode{fetch_fminimum_num},
 the maximum and minimum computation is performed
 as if by \tcode{fmaximum_num} and \tcode{fminimum_num}, respectively,
 with the value pointed to by \tcode{this} and the first parameter