Trailing slashes on galaxy_url_prefix are no longer stripped/collapsed after upgrade to starlette 0.35.1

[natefoo]

Describe the bug
After the starlette upgrade in 0c0da9c, trailing slashes in galaxy_url_prefix are no longer stripped/collapsed/ignored as they were before. As a result, if set to /prefix/, the URL must also contain the trailing slash, e.g. http://localhost:8080/prefix//api/version or you get a 404.

Galaxy Version and/or server at which you observed the bug
Galaxy Version: 24.0 dev
Commit: 9c3a020

To Reproduce
Steps to reproduce the behavior:

1. Set galaxy_url_prefix: /prefix/ in galaxy.yml
2. Start galaxy and curl http://localhost:8080/prefix/api/version (fails), then curl http://localhost:8080/prefix//api/version (succeeds)
3. Downgrade to 24b90be and pip install -r requirements.txt
4. Start galaxy and repeat curls, both succeed.

Expected behavior
Trailing slashes are not required to be part of the URL.

Screenshots
N/A

Additional context
This was initially caught by the tests on galaxyproject/gravity#116