Fix a bug with moving dock left and right.
Fix a bug with moving dock left and right.

Fixes #67039

`get_index` counts internal children by default but `move_child` ignores them therefore `move_child` had no effect.

The call to `set_current_tab` is not needed anymore in Godot 4 since the current tab will change when calling `move_child`.

josempans/godot,pkowal1982/godot,godotengine/godot,vkbsb/godot,guilhermefelipecgs/godot,vkbsb/godot,guilhermefelipecgs/godot,godotengine/godot,josempans/godot,guilhermefelipecgs/godot,guilhermefelipecgs/godot,pkowal1982/godot,pkowal1982/godot,josempans/godot,pkowal1982/godot,sanikoyes/godot,BastiaanOlij/godot,vkbsb/godot,pkowal1982/godot,sanikoyes/godot,josempans/godot,BastiaanOlij/godot,josempans/godot,godotengine/godot,godotengine/godot,BastiaanOlij/godot,guilhermefelipecgs/godot,josempans/godot,guilhermefelipecgs/godot,godotengine/godot,sanikoyes/godot,godotengine/godot,sanikoyes/godot,vkbsb/godot,BastiaanOlij/godot,BastiaanOlij/godot,sanikoyes/godot,godotengine/godot,josempans/godot,BastiaanOlij/godot,vkbsb/godot,vkbsb/godot,BastiaanOlij/godot,sanikoyes/godot,sanikoyes/godot,vkbsb/godot,pkowal1982/godot,pkowal1982/godot,godotengine/godot,BastiaanOlij/godot,guilhermefelipecgs/godot,guilhermefelipecgs/godot,josempans/godot,vkbsb/godot,sanikoyes/godot,pkowal1982/godot