Can't multi-edit time value for a keyframe

### Tested versions

4.3-stable

### System information

Windows

### Issue description

I can't set a time value for multiple keyframes (I'm trying to move them in bulk)


### Steps to reproduce

Create an animation with multiple keyframes, select keyframes, see the "time" opdion disappear from multiedit

### Minimal reproduction project (MRP)

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Reproduce the issue in Godot 4.3-stable on Windows by creating an animation, selecting multiple keyframes, and checking the multi-edit controls. Trace the animation editor's multi-selection handling; done when the time value remains available and selected keyframes can be moved in bulk.

Written by the indexing model from the issue text.