fix bad manpage cross reference format

sys/man/3/shr

@@ -50,7 +50,7 @@ on the mount tree.
 The service file can be reopened and passed to
 .IR mount
 (see
-.IR bind(2))
+.IR bind (2))
 or added to another share.
 .PP
 Multiple services can be mounted under a share forming a union

sys/man/4/rio

@@ -129,7 +129,7 @@ Closing the file makes the window revert to default state
 .TP
 .B kbd
 represents the raw keyboard events (see
-.IR kbdfs(8))
+.IR kbdfs (8))
 for the corresponding window. While open,
 navigation keys and input on the
 .IR cons

sys/man/8/boot

@@ -104,7 +104,7 @@ bootargs is (tcp, local!device)[/dev/sdC0/fscache]:
 A newline picks the default. Entering
 .B !rc
 breaks into the
-.IR rc(1)
+.IR rc (1)
 shell.
 Other possible responses are
 .I method