Simplify dock_sled()

`dock_sled()` is never called with offset parameter - remove it.
We move x only - so only that needs to be homed. Consequence is - we can home to z-min now with a sled probe!
Feedrates are set and restored in `do_blocking_move()`.
We already checked if the probe is deployed/stowed in deploy/stow_probe.
```
if (z_loc < _Z_RAISE_PROBE_DEPLOY_STOW + 5) z_loc = _Z_RAISE_PROBE_DEPLOY_STOW;
```
makes no sense - remove.
Now the raise is the same for deploy/stow -> move before the if.
Replace the if with a ternary.
Instead writing LOW/HIGH use the boolean `stow` we already have.

There is no reason for not using the sled probe in G29/M48 with 'E'.
It takes a while but works. (tested!)