remove advice re seeding keyring backends (#9164)

(cherry picked from commit 75453c2)

docs/repositories.md

@@ -532,12 +532,6 @@ Microsoft's [artifacts-keyring](https://pypi.org/project/artifacts-keyring/) get
 valid credentials. It will need to be properly installed into Poetry's virtualenv,
 preferably by installing a plugin.
 
-If you are letting Poetry manage your virtual environments you will want a virtualenv
-seeder installed in Poetry's virtualenv that installs the desired keyring backend
-during `poetry install`. To again use Azure DevOps as an example: [azure-devops-artifacts-helpers](https://pypi.org/project/azure-devops-artifacts-helpers/)
-provides such a seeder. This would of course best achieved by installing a Poetry plugin
-if it exists for you use case instead of doing it yourself.
-
 {{% /note %}}
 
 Alternatively, you can use environment variables to provide the credentials: