Fix inconsistent deployment concurrency limit documentation

[EmilRex]

This concurrency limit fields section of the docs suggests that the deployment YAML has the following structure:

deployments:
  ...
  concurrency_limit:
    limit: <int>
    collision_strategy: <str>

When in fact it has the following structure:

deployments:
  ...
  concurrency_limit: <int>
  concurrency_options:
    collision_strategy: <str>

This also slightly conflicts with the documentation here.