change .PP to .IP in description of Open.

Reference: /n/sources/patch/applied/9p-man-typo
Date: Tue Jul  6 05:22:59 CES 2004

--- /sys/man/2/9p	Tue Jul  6 05:22:59 2004
+++ /sys/man/2/9p	Tue Jul  6 05:22:59 2004
@@ -444,7 +444,7 @@
 metadata will be consulted on open, create, remove, and wstat
 to see if the requester has the appropriate permissions.
 If not, an error will be sent back without consulting a service function.
-.PP
+.IP
 If not using file trees or the user has the appropriate permissions,
 .I open
 is called with