#1535 Test Matrix operations: correct a path oin Lua file to make it work on Linux.

Sources/Test/ThirdParty/PETSc/MatrixOperations/demo.lua

@@ -160,7 +160,7 @@ Result = {
 	-- directly: it might have been extended in MoReFEMData class! Rather call the GetResultDirectory() from 
 	-- this class. 
 	-- Expected format: "VALUE"
-	output_directory = "${MOREFEM_RESULT_DIR}/Test/ThirdParty/Petsc/MatrixOperations",
+	output_directory = "${MOREFEM_TEST_OUTPUT_DIR}/Test/ThirdParty/Petsc/MatrixOperations",
 
 	-- Enables to skip some printing in the console. Can be used to WriteSolution every n time.
 	-- Expected format: VALUE