fix: incorrect callback association when choosing --emg-mode=3 and with IMU

The callback registration is not associated right:

```console
future: exception=TypeError('can only concatenate tuple (not "IMUData") to tuple')>
Traceback (most recent call last):
File "/Users/iomz/ghq/github.com/iomz/dl-myo/myo/core.py", line 393, in notify_callback
await self.on_imu_data(IMUData(data))
File "/Users/iomz/ghq/github.com/Interactions-HSG/MyoKTROS/src/myoktros/client.py", line 207, in on_imu_data
line = ",".join(map(str, (time.time(),) + imu))
TypeError: can only concatenate tuple (not "IMUData") to tuple
2023-08-23 09:11:20,027 asyncio ERROR: Task exception was never retrieved
future: exception=NotImplementedError()>
Traceback (most recent call last):
File "/Users/iomz/ghq/github.com/iomz/dl-myo/myo/core.py", line 407, in notify_callback
await self.on_emg_data(emg)
File "/Users/iomz/ghq/github.com/iomz/dl-myo/myo/core.py", line 358, in on_emg_data
raise NotImplementedError()
NotImplementedError
```

Start with the callback dispatch in myo/core.py around lines 375-407 and the IMU handling in src/myoktros/client.py around line 207. Reproduce the issue using --emg-mode=3 with an IMU, then trace how IMU and EMG callbacks are associated; done means the intended callbacks receive the correct data and the reported TypeError and NotImplementedError no longer occur.

Written by the indexing model from the issue text.