/usr/share/gconf/defaults/10_metacity-common is in metacity-common 1:2.34.1-1ubuntu11.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | /apps/metacity/general/num_workspaces 4
/apps/metacity/global_keybindings/switch_windows_backward <Shift><Alt>Tab
/apps/metacity/global_keybindings/run_command_terminal <Control><Alt>t
/apps/metacity/global_keybindings/show_desktop <Control><Super>d
/apps/metacity/window_keybindings/maximize <Control><Super>Up
/apps/metacity/window_keybindings/unmaximize <Control><Super>Down
/apps/metacity/window_keybindings/toggle_maximized <Control><Alt>KP_5
/apps/metacity/window_keybindings/minimize <Control><Alt>KP_0
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