[geomech][test] Replace obsolete dgf files by input file

test/geomechanics/el1p2c/grids/test_el1p2c.dgf

-DGF
-Interval
-0 0 0  % first corner 
-10 10 10  % second corner
-4 4 4  % cells in x y z direction
-# 
-
-BOUNDARYDOMAIN
-default 1    % all boundaries have id 1
-#BOUNDARYDOMAIN
-# unitcube.dgf 

test/geomechanics/el1p2c/test_el1p2c.input

@@ -6,5 +6,5 @@ TEnd = 1e4 # [s]
 EnableGravity = 0
 
 [Grid]
-File = grids/test_el1p2c.dgf
-
+UpperRight = 10 10 10
+Cells = 4 4 4

test/geomechanics/el2p/grids/test_el2p.dgf

-DGF
-Interval
-0 0 0  % first corner 
-1000 1000 1000  % second corner
-4 4 4   % 1 cells in x and 1 in y direction
-# 
-
-BOUNDARYDOMAIN
-default 1    % all boundaries have id 1
-#BOUNDARYDOMAIN
-# unitcube.dgf 

test/geomechanics/el2p/test_el2p.input

@@ -5,8 +5,9 @@ DtInitial = 10       # [s]
 EpisodeLength = 1e6  # [s]
 
 [Grid]
-File = ./grids/test_el2p.dgf
-Refine = 0
+UpperRight = 1000 1000 1000
+Cells = 4 4 4
+Refinement = 0
 
 [Injection]
 DepthBOR = 2000     # Depth at the bottom of the scenario [m]