Broken links for "Accessing Shoot Clusters"

[MartinWeindel]

What happened:

Links pointing to https://github.com/gardener/gardener/blob/master/docs/usage/shoot_access.md are broken. An additional subdirectory has been introduced. They new link is
https://github.com/gardener/gardener/blob/master/docs/usage/shoot/shoot_access.md

There are at least two places:

1. Create Cluster page / Cluster Details / Enable static token kubeconfig / link "secure alternatives"

2. Documentation page
   

   dashboard/docs/usage/project-operations.md

   Line 335 in e9b3788

   - You can obtain a temporary admin `kubeconfig` by using the `shoots/admin/kubeconfig` subresource. Detailed instructions can be found in the Gardener documentation [here](https://github.com/gardener/gardener/blob/master/docs/usage/shoot_access.md#shootsadminkubeconfig-subresource).

What you expected to happen:

Links should point to https://github.com/gardener/gardener/blob/master/docs/usage/shoot/shoot_access.md

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know:

Environment: