Remove unused variable in usr.bin/systat/main.c

[evh]

int ms in cmd_count is unused as of 1.63

Index: main.c
===================================================================
RCS file: /cvs/src/usr.bin/systat/main.c,v
retrieving revision 1.63
diff -u -p -r1.63 main.c
--- main.c      18 Apr 2015 18:28:38 -0000      1.63
+++ main.c      1 Jan 2016 19:26:39 -0000
@@ -297,7 +297,6 @@ void
 cmd_count(const char *buf)
 {
        const char *errstr;
-       int ms;
 
        maxprint = strtonum(buf, 1, lines - HEADER_LINES, &errstr);
        if (errstr)