[T] Converted Linear_Disc_with_hole notebook to markdown

  pipx run jupytext --to markdown Tests/Data/Mechanics/Linear/DiscWithHole/Linear_Disc_with_hole.ipynb

ProcessLib/SmallDeformation/Tests.cmake

@@ -269,7 +269,7 @@ AddTest(
 
 if(NOT OGS_USE_PETSC)
     NotebookTest(NOTEBOOKFILE Mechanics/Linear/SimpleMechanics.ipynb RUNTIME 5)
-    NotebookTest(NOTEBOOKFILE Mechanics/Linear/DiscWithHole/Linear_Disc_with_hole.ipynb RUNTIME 15)
+    NotebookTest(NOTEBOOKFILE Mechanics/Linear/DiscWithHole/Linear_Disc_with_hole.md RUNTIME 15)
     if(NOT WIN32)
         NotebookTest(NOTEBOOKFILE Mechanics/Linear/DiscWithHole/Linear_Disc_with_hole_convergence_analysis.ipynb RUNTIME 40)
     endif()