[T/HM] Slightly relax ctest's tolerance

Tests/Data/HydroMechanics/ExcavationNiches/excavation_niches.prj

@@ -296,7 +296,7 @@
         <vtkdiff>
             <regex>excavation_niches_ts_.*.vtu</regex>
             <field>pressure</field>
-            <absolute_tolerance>6e-8</absolute_tolerance>
+            <absolute_tolerance>7e-8</absolute_tolerance>
             <relative_tolerance>1e-15</relative_tolerance>
         </vtkdiff>
         <vtkdiff>