fix gdal_contour in test

now gdal_contour does not create 3D by default
see upstream issue OSGeo/gdal#336
and fix OSGeo/gdal@abae82c

Author: 3nids

python/plugins/processing/tests/testdata/gdal_algorithm_tests.yaml

@@ -109,6 +109,7 @@ tests:
       BAND: 1
       CREATE_3D: false
       FIELD_NAME: ELEV
+      CREATE_3D: true
       IGNORE_NODATA: false
       INPUT:
         name: dem.tif