chore(deps): Update prompt-toolkit requirement in /demo

Updates the requirements on [prompt-toolkit](https://github.com/prompt-toolkit/python-prompt-toolkit) to permit the latest version.
- [Release notes](https://github.com/prompt-toolkit/python-prompt-toolkit/releases)
- [Changelog](https://github.com/prompt-toolkit/python-prompt-toolkit/blob/main/CHANGELOG)
- [Commits](prompt-toolkit/python-prompt-toolkit@2.0.10...3.0.51)

---
updated-dependencies:
- dependency-name: prompt-toolkit
  dependency-version: 3.0.51
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

demo/requirements.txt

@@ -1,5 +1,5 @@
 asyncpg~=0.30.0
-prompt_toolkit~=2.0.10
+prompt_toolkit~=3.0.51
 web.py~=0.62
 pygments~=2.19
 qrcode[pil]~=8.1