Revert "Issue #15824: waterpixels filter on a selection appears to hang GIMP."

This reverts commit d91a8b2abe.

As reported by Liam on #15824, this commit was clearly wrong and
reintroduced the old cropping bug with multiple filters. Reverting.

The next commit was likely good, though the real hanging bug is — as far
as my test go — in the GEGL op itself. This second commit 75e665f0ed was
improving things, but obviously, as the bug is still in the op, it can
still be triggered. We'll have to fix the source bug next.

app/core/gimpdrawablefilter.c

@@ -1460,11 +1460,16 @@ gimp_drawable_filter_sync_region (GimpDrawableFilter *filter)
                          "y", (gdouble) -filter->filter_area.y,
                          NULL);
 
-          gegl_node_set (filter->crop_before,
-                         "operation", "gegl:crop",
-                         "width",     (gdouble) filter->filter_area.width,
-                         "height",    (gdouble) filter->filter_area.height,
-                         NULL);
+          if (first_filter)
+            gegl_node_set (filter->crop_before,
+                           "operation", "gegl:crop",
+                           "width",     (gdouble) filter->filter_area.width,
+                           "height",    (gdouble) filter->filter_area.height,
+                           NULL);
+          else
+            gegl_node_set (filter->crop_before,
+                           "operation", "gegl:nop",
+                           NULL);
         }
 
       if (filter->filter_clip)