[BUG] OOM when invoking normalize_characters on a relatively small dataframe

**Describe the bug**
Hi, I am facing the following OOM when invoking normalize_characters() on a relatively small dataset, which uses less than 2 GB of VRAM on a 16GB v100.

In case it helps, normalize_spaces() works without issues in the same dataframe.

Please, find below how to reproduce it.


**Steps/Code to reproduce bug**

> import cudf
> import pandas as pd
>
> df = cudf.DataFrame({"text": pd.util.testing.rands_array(256, 5000000)})
> #df["text"] = df["text"].str.normalize_spaces()
> df["text"] = df["text"].str.normalize_characters(do_lower=False)
>

**Expected behavior**
No OOM

**Environment overview (please complete the following information)**
- Environment location: [Bare-metal, Docker, Cloud(specify cloud provider)]
- Method of cuDF install: [conda, Docker, or from source]
- If method of install is [Docker], provide `docker pull` & `docker run` commands used

**Environment details**
DGX-v100, cudf 22.04