[partial.sort] Remove 'It takes' from complexity specification.

Partially addresses #1088.

Author: jensmaurer

source/algorithms.tex

@@ -3716,7 +3716,7 @@
 
 \pnum
 \complexity
-It takes approximately
+Approximately
 \tcode{(last - first) * log(middle - first)}
 comparisons.
 \end{itemdescr}