Physics Interpolation - Fix project setting tooltip

[lawnjelly]

Corrects a confusing documentation which refers to physics objects, whereas FTI applies to all rendered objects.

Fixes tooltip documentation mentioned in #104423

Bugsquad edit: Closes #104423.

Notes

• Also removes the jitter fix section which is now out of date (it gets set to 0.0 automatically at startup when physics interpolation is on).

[Mickeon]

it gets set to 0.0 automatically at startup when physics interpolation is on).

Then that's exactly what should be said, instead.

Also this description is duplicated in SceneTree's physics_interpolation property, so it should be changed there as well

[lawnjelly]

Then that's exactly what should be said, instead.
Also this description is duplicated in SceneTree's physics_interpolation property, so it should be changed there as well

Done. I've also expanded the section into a note on physics_interpolation_mode as it makes sense to make it clear here that the global setting can be overridden per branch, this is not obvious to a lot of users.

[fire]

Not deep into physics, but if the physics contributors needs a review I approve.

[akien-mga]

Thanks!