Change ref value for test 31 from 3000 to 4000.

This is another side effect of the changes in Math and this difference must be
investigated.


git-svn-id: http://root.cern.ch/svn/root/trunk@22532 27541ba8-7e3a-0410-8455-c3a389f83636

test/stressGraphics.ref

@@ -29,7 +29,7 @@ Test#   PS1Ref#   PS1Err#   PDFRef#   PDFErr#   GIFRef#   GIFErr#   JPGRef#   JP
    28    212209      6500    102059       300     37205     10400     61488     34100     43309     14000    217794      6500
    29    249838      5000    130588       750     41146      6300     62322     31800     50523      6500    254272      5000
    30   1478954     35000    756419       200     79983      3400     71921      9900    102436      3500   1506403     35000
-   31    298701      2000    170799      3000     28920      8600     38340     13500     38337     18100    299977      2000
+   31    298701      2000    170799      4000     28920      8600     38340     13500     38337     18100    299977      2000
    32     23432       200     47599       100     21317      3900     37157     11800     33312      8000     23278       200
    33     14936       100     28567       100     34096      1500     42564     11300     33475      3900     14711       100
    34    255911      3000    375135       100     35230      5000     56595     30400     46201      6500    260242      3000