Set 'ytics 1' for files graph.

This prevents tics like 1.75, 2.5 etc on file count / y-axis.

Reported by Anonymous on SourceForge bug #2892604.

gitstats

@@ -874,6 +874,7 @@ set timefmt "%Y-%m-%d"
 set format x "%Y-%m-%d"
 set ylabel "Files"
 set xtics rotate by 90
+set ytics 1
 set bmargin 6
 plot 'files_by_date.dat' using 1:2 w steps
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