Fix typo in usage docstring

s/fd_stats/fd_status/

Author: itamaro

Lib/test/subprocessdata/fd_status.py

@@ -2,7 +2,7 @@
 file descriptors on stdout.
 
 Usage:
-fd_stats.py: check all file descriptors (up to 255)
+fd_status.py: check all file descriptors (up to 255)
 fd_status.py fd1 fd2 ...: check only specified file descriptors
 """