Problem changing Chatbot text size in Blocks

[ZQ-Dev8]

Describe the bug

Reporting a potential bug where lowering the text size via gr.Blocks(theme = gr.themes.Default(text_size='sm',)) does not affect the size of the text in the chatbot. Oddly, this does work when increasing the text size to lg, but values of sm (and presumably lower) are ignored. See attached reproduction and screenshots for reference.

Have you searched existing issues? 🔎

• I have searched and found no existing issues

Reproduction

import gradio as gr
import random
import time

# text_size='sm' is ignored (see screenshot 1) while text_size='lg' is obeyed (see screenshot 2)
with gr.Blocks(theme = gr.themes.Default(text_size='sm',)) as demo:
# with gr.Blocks(theme = gr.themes.Default(text_size='lg',)) as demo:
    chatbot = gr.Chatbot()
    msg = gr.Textbox()
    clear = gr.ClearButton([msg, chatbot])

    def respond(message, chat_history):
        bot_message = random.choice(["How are you?", "I love you", "I'm very hungry"])
        chat_history.append((message, bot_message))
        time.sleep(2)
        return "", chat_history

    msg.submit(respond, [msg, chatbot], [msg, chatbot])

if __name__ == "__main__":
    demo.launch()
    ```

### Screenshot

![ss1](https://github.com/gradio-app/gradio/assets/6372983/b35351c2-516c-4516-873f-d67a02301c39)
![ss2](https://github.com/gradio-app/gradio/assets/6372983/ac1c0b62-2199-49ee-851f-b2284fd72317)


### Logs

```shell
No error message to report.

System Info

Gradio Environment Information:
------------------------------
Operating System: Linux
gradio version: 4.11.0
gradio_client version: 0.7.3

------------------------------------------------
gradio dependencies in your environment:

aiofiles: 23.2.1
altair: 5.1.2
fastapi: 0.104.1
ffmpy: 0.3.1
gradio-client==0.7.3 is not installed.
httpx: 0.25.0
huggingface-hub: 0.19.4
importlib-resources: 6.1.0
jinja2: 3.1.2
markupsafe: 2.1.3
matplotlib: 3.8.1
numpy: 1.26.1
orjson: 3.9.10
packaging: 23.2
pandas: 2.1.2
pillow: 10.1.0
pydantic: 2.4.2
pydub: 0.25.1
python-multipart: 0.0.6
pyyaml: 6.0.1
semantic-version: 2.10.0
tomlkit==0.12.0 is not installed.
typer: 0.9.0
typing-extensions: 4.8.0
uvicorn: 0.23.2
authlib; extra == 'oauth' is not installed.
itsdangerous; extra == 'oauth' is not installed.


gradio_client dependencies in your environment:

fsspec: 2023.10.0
httpx: 0.25.0
huggingface-hub: 0.19.4
packaging: 23.2
typing-extensions: 4.8.0
websockets: 11.0.3

### Severity

I can work around it

[ZQ-Dev8]

Issue derived from this brief HF Discord conversation, for reference - https://discord.com/channels/879548962464493619/1187532601225912430

[hannahblair]

I can repro this. Thanks for raising this, we'll look into it!