Update documentation to remove adhoc and playbook refs

[Shrews]

Remove remaining references to the adhoc and playbook subcommands that were previously removed.

Fixes: #753

[ansible-zuul]

LGTM!

[patchback]

Backport to release_2.1: 💚 backport PR created

✅ Backport PR branch: patchback/backports/release_2.1/c254516d1fc96cc8cc26661f30f127da5d28691d/pr-870

Backported as #875

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[patchback]

Backport to release_2.0: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply c254516 on top of patchback/backports/release_2.0/c254516d1fc96cc8cc26661f30f127da5d28691d/pr-870

Backporting merged PR #870 into devel

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/ansible/ansible-runner.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/release_2.0/c254516d1fc96cc8cc26661f30f127da5d28691d/pr-870 upstream/release_2.0

4. Now, cherry-pick PR Update documentation to remove adhoc and playbook refs #870 contents into that branch:

   $ git cherry-pick -x c254516d1fc96cc8cc26661f30f127da5d28691d

   If it'll yell at you with something like fatal: Commit c254516d1fc96cc8cc26661f30f127da5d28691d is a merge but no -m option was given., add -m 1 as follows intead:

   $ git cherry-pick -m1 -x c254516d1fc96cc8cc26661f30f127da5d28691d

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Update documentation to remove adhoc and playbook refs #870 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/release_2.0/c254516d1fc96cc8cc26661f30f127da5d28691d/pr-870

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.