Fix indentation. (#365)

docs/collection-docs.md

@@ -71,7 +71,8 @@ This subcommand has multiple options which allow to control validation. The most
 * `--plugin-docs`: whether to validate schemas and markup of modules, plugins, and roles included in the collection. By default, this is not run (for backwards compatibility). We recommend to always specify this.
 * `--validate-collection-refs {self,dependent,all}`: Specify how to validate inter-plugin/module/role and inter-collection references in plugin/module/role documentation. This covers Ansible markup, like `M(foo.bar.baz)` or `O(foo.bar.baz#module:parameter=value)`, and other links such as `seealso` sections. If set to `self`, only references to the same collection are validated. If set to `dependent`, only references to the collection itself and collections it (transitively) depends on are validated, including references to ansible-core (as `ansible.builtin`). If set to `all`, all references to other collections are validated.
 
-  If collections are referenced that are not installed and that are in scope, references to them will not be reported. Reporting these can be enabled by specifying `--disallow-unknown-collection-refs`.
+    If collections are referenced that are not installed and that are in scope, references to them will not be reported. Reporting these can be enabled by specifying `--disallow-unknown-collection-refs`.
+
 * `--skip-rstcheck`: by default, when specifying `--plugin-docs`, antsibull-docs generates RST documentation for module/plugin/role docs and runs [`rstcheck`](https://rstcheck.readthedocs.io/) on these. This step is usually not necessary, since it will mostly point out errors in antsibull-docs' RST generation code, and will slow down linting especially for large collections.
 * `--disallow-semantic-markup`: If you want to avoid semantic markup in Ansible markup, for example for collections whose documentation must render OK with older versions of ansible-doc or Automation Hub, you can use this parameter to make antsibull-docs report all markup that is not supported. Semantic markup is supported by ansible-doc since ansible-core 2.15.0.