Allow all hosts in jupyter-server-proxy

[jasonkena]

Allows the dashboard for remote workers on the bokeh info page to function by modifying host_allowlist.

This solves the error Host 'xxx' is not allowed. See https://jupyter-server-proxy.readthedocs.io/en/latest/arbitrary-ports-hosts.html for info.

• Tests added / passed
• Passes pre-commit run --all-files

[GPUtester]

Can one of the admins verify this patch?

Admins can comment ok to test to allow this one PR to run or add to allowlist to allow all future PRs from the same author to run.

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

       15 files  ±0         15 suites  ±0   6h 48m 0s ⏱️ + 5m 57s
  3 086 tests ±0    3 001 ✔️ ±0    84 💤 ±0  1 ❌ ±0 
22 834 runs  ±0  21 848 ✔️ ±0  985 💤 ±0  1 ❌ ±0 

For more details on these failures, see this check.

Results for commit 64410d9. ± Comparison against base commit bfc5cfe.

[jacobtomlinson]

I am apprehensive to just set this to True and allow all proxying. This feature of jupyter-server-proxy is intended to avoid folks from using the proxy to access services they shouldn't.

Ideally we should just be adding the worker IPs to the allowlist.

cc @yuvipanda who may have opinions here