LayoutLMV3 Tokenizer Inserts Odd Characters
### System Info

(This is on a fresh google colab instance)
- `transformers` version: 4.21.2
- Platform: Linux-5.4.188+-x86_64-with-Ubuntu-18.04-bionic
- Python version: 3.7.13
- Huggingface_hub version: 0.9.1
- PyTorch version (GPU?): 1.12.1+cu113 (True)
- Tensorflow version (GPU?): 2.8.2 (True)
- Flax version (CPU?/GPU?/TPU?): not installed (NA)
- Jax version: not installed
- JaxLib version: not installed
- Using GPU in script?: no
- Using distributed or parallel set-up in script?: no


### Who can help?

@NielsRogge 

### Information

- [X] The official example scripts
- [ ] My own modified scripts

### Tasks

- [X] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...)
- [ ] My own task or dataset (give details below)

### Reproduction

```
from transformers import LayoutLMv3TokenizerFast

tok = LayoutLMv3TokenizerFast.from_pretrained('microsoft/layoutlmv3-base')

tok.tokenize('Hello world')
>>> ['ĠHello', 'Ġworld']
```

### Expected behavior

The special characters are not expected when calling tokenize(). This doesn't happen when using the LayoutLMV2 tokenizer.
@logan-markewich -- have a look at this [entry in our forum](https://discuss.huggingface.co/t/bpe-tokenizers-and-spaces-before-words/475/2?u=joaogante)<|||||>@gante Yea ok, that gives some context for what is actually going on

I guess I will just need to remove those characters myself? A little annoying, but oh well<|||||>Hi,

No that's just the way tokenization happens. The tokenization is based on Byte Pair Encoding (BPE) algorithm. This is also used by RoBERTa for instance. 

You can check out the Huggingface course if you want to learn about this: https://huggingface.co/course/chapter6/5?fw=pt