UI: move playhead snapping to footer

This patch moves the playhead snapping UI element to the
new footer introduced with 35bcbad7e9
This is in preparation for removing the timeline editor, see #131102

Pull Request: https://projects.blender.org/blender/blender/pulls/144922

scripts/startup/bl_ui/space_graph.py

@@ -9,13 +9,6 @@ from bl_ui.space_dopesheet import (
     dopesheet_filter,
 )
 from bl_ui.space_time import playback_controls
-from bl_ui.utils import (
-    PlayheadSnappingPanel,
-)
-
-
-class GRAPH_PT_playhead_snapping(PlayheadSnappingPanel, Panel):
-    bl_space_type = 'GRAPH_EDITOR'
 
 
 def drivers_editor_footer(layout, context):
@@ -95,11 +88,6 @@ class GRAPH_HT_header(Header):
                 text="",
             )
 
-            row = layout.row(align=True)
-            row.prop(tool_settings, "use_snap_playhead", text="")
-            sub = row.row(align=True)
-            sub.popover(panel="GRAPH_PT_playhead_snapping", text="")
-
         row = layout.row(align=True)
         row.prop(tool_settings, "use_proportional_fcurve", text="", icon_only=True)
         sub = row.row(align=True)
@@ -611,7 +599,6 @@ classes = (
     GRAPH_PT_filters,
     GRAPH_PT_snapping,
     GRAPH_PT_driver_snapping,
-    GRAPH_PT_playhead_snapping,
 )
 
 if __name__ == "__main__":  # only for live edit.