Increase test tolerence
Increase test tolerence

Test fails on aarch64 and ppc64le on Fedora 30 and Fedora rawhide:
Test  3 : Purge, Reuse of gaps in TFile......................... FAILED
         File size= 52010 (expected 51886 +/- 100)
         Comp Fact=  2.00 (expected 2.1 +/- 0.3)

olifre/root,karies/root,karies/root,olifre/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,karies/root,olifre/root,karies/root,karies/root,karies/root,olifre/root,olifre/root,olifre/root,root-mirror/root,olifre/root,karies/root,karies/root,karies/root,root-mirror/root,karies/root,root-mirror/root