No more DPI adjusting

Closes #191 (closed)

Needs testing on a real dataset because training test is failing only because optimizers are different.

docs/usage/train/config.md

@@ -134,7 +134,8 @@ The following configuration is used by default when using the `teklia-dan train`
 ```py
 transforms = A.Compose(
     [
-        DPIAdjusting(min_factor=0.75, max_factor=1),
+        # Scale between 0.75 and 1.0
+        RandomScale(scale_limit=[-0.25, 0], always_apply=True, interpolation=cv2.INTER_AREA),
         A.SomeOf(
             [
                 ErosionDilation(min_kernel=1, max_kernel=4, iterations=1),