Bumping dependency to ProxyManager to allow testing against the new 0.5.x versions

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | no (looks like an unrelated failure, though)
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

Nothing to see here. Move along.