Update title-blocks.qmd

I think it's just doi, not doi-title

Author: melaniewalsh

docs/authoring/title-blocks.qmd

@@ -89,7 +89,7 @@ The labels for the metadata included in the title block have default values that
 | `abstract-title`    | Abstract       | `plain`, `default`, `none` |
 | `description-title` | Description    | `plain`, `default`         |
 | `published-title`   | Date Published | `plain`, `default`         |
-| `doi-title`         | DOI            | `plain`, `default`         |
+| `doi`         | DOI            | `plain`, `default`         |
 
 ## Custom Title Pages