gsettings set org.gnome.Terminal.Legacy.Keybindings:/org/gnome/terminal/legacy/keybindings/ next-tab '<Primary>Tab'
gsettings set org.gnome.Terminal.Legacy.Keybindings:/org/gnome/terminal/legacy/keybindings/ prev-tab '<Primary><Shift>Tab'

# new method with dconf
dconf write /org/gnome/terminal/legacy/keybindings/next-tab "'<Primary>Tab'"
dconf write /org/gnome/terminal/legacy/keybindings/prev-tab "'<Primary><Shift>Tab'"

# checking settings
dconf read /org/gnome/terminal/legacy/keybindings/next-tab
dconf read /org/gnome/terminal/legacy/keybindings/prev-tab

# list settings keys
dconf list /org/gnome/terminal/legacy/
dconf list /org/gnome/terminal/legacy/keybindings/