Fix #118263: VSE: Expose remove all gaps in UI

Add `gap_remove` operator with `all` property true in `Strips >
Transform` menu

Pull Request: https://projects.blender.org/blender/blender/pulls/131485

scripts/startup/bl_ui/space_sequencer.py

@@ -885,6 +885,7 @@ class SEQUENCER_MT_strip_transform(Menu):
 
             layout.separator()
             layout.operator("sequencer.gap_remove").all = False
+            layout.operator("sequencer.gap_remove", text="Remove Gaps (All)").all = True
             layout.operator("sequencer.gap_insert")