Do plot grid bounding box if not `uniform_lon_lat`

Do not try to plot grid bounding box if not `uniform_lon_lat`, for
now.

Inst_eddies/Analysis/plot_eddy_contours.py

@@ -140,7 +140,7 @@ def snapshot(
 def plot_grid_bb(grid_nml, ax):
     """Grid bounding box."""
 
-    if grid_nml is not None:
+    if grid_nml is not None and grid_nml["UNIFORM_LON_LAT"]:
         step = grid_nml["STEP_DEG"]
         rect = patches.Rectangle(
             grid_nml["corner_deg"],