man tc-htb: Fix HRB -> HTB typo

Changed HRB -> HTB.

Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
diff --git a/man/man8/tc-htb.8 b/man/man8/tc-htb.8
index d196ecd..95f25de 100644
--- a/man/man8/tc-htb.8
+++ b/man/man8/tc-htb.8
@@ -48,7 +48,7 @@
 .B tc-tbf (8).
 
 .SH CLASSIFICATION
-Within the one HRB instance many classes may exist. Each of these classes
+Within the one HTB instance many classes may exist. Each of these classes
 contains another qdisc, by default 
 .BR tc-pfifo (8).