Update ipyleaflet/velocity.py

Co-authored-by: David Brochart <david.brochart@gmail.com>

Author: HaudinFlorence

ipyleaflet/velocity.py

@@ -76,7 +76,7 @@ def _default_color_scale(self):
 
         for color in self.colormap.colors:
             rgb_tuple = tuple(int(x * 256) for x in color[:3])
-            rgb_str = f'rgb{str(rgb_tuple)}'
+            rgb_str = f"rgb{rgb_tuple}"
             self.color_scale.append(rgb_str)
 
         return self.color_scale