Fix #136538: Grease Pencil: Remove unused "Sample Color" keymap

This was meant to be used by GPv3, but ended up also being called
from GPv2 Draw Mode.
Removes the entry since it's not doing anything.

Pull Request: https://projects.blender.org/blender/blender/pulls/136599

scripts/presets/keyconfig/keymap_data/blender_default.py

@@ -4588,8 +4588,6 @@ def km_grease_pencil_paint_mode(_params):
         # Show/hide
         *_template_items_hide_reveal_actions("grease_pencil.layer_hide", "grease_pencil.layer_reveal"),
 
-        ("paint.sample_color", {"type": 'X', "value": 'PRESS', "shift": True}, None),
-
         # Isolate Layer
         ("grease_pencil.layer_isolate", {"type": 'NUMPAD_ASTERIX', "value": 'PRESS'}, None),
     ])