man: fix incorrect use of "it's"

A couple of places were using "it's" where possive form "its"
should be used instead.

man/man7/tc-hfsc.7

@@ -320,7 +320,7 @@ UL criterion is an extensions to LS one, that permits sending packets only
 if current real time is bigger than fit\-time ('ft'). So the modified LS
 criterion becomes: choose the smallest virtual time from all active children,
 such that fit\-time < current real time also holds. Fit\-time is calculated
-from F(), which is based on UL service curve. As you can see, it's role is
+from F(), which is based on UL service curve. As you can see, its role is
 kinda similar to E() used in RT criterion. Also, for obvious reasons \- you
 can't specify UL service curve without LS one.
 

man/man8/ip-netns.8

@@ -25,7 +25,7 @@ ip-netns \- process network namespace management
 
 .SH DESCRIPTION
 A network namespace is logically another copy of the network stack,
-with it's own routes, firewall rules, and network devices.
+with its own routes, firewall rules, and network devices.
 
 By convention a named network namespace is an object at
 .BR "/var/run/netns/" NAME