docs: remove references to removed utility API docs

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

docs/auth/index.md

@@ -60,9 +60,8 @@ small update to show this provider as a login option. The `SignInPage` component
 handles this, and takes either a `provider` or `providers` (array) prop of
 `SignInProviderConfig` definitions.
 
-These reference the [ApiRef](../reference/utility-apis/README.md) exported by
-the provider. Again, an example using GitHub that can be adapted to any of the
-built-in providers:
+These reference the `ApiRef` exported by the provider. Again, an example using
+GitHub that can be adapted to any of the built-in providers:
 
 ```diff
 # packages/app/src/App.tsx

docs/auth/using-auth.md

@@ -28,7 +28,8 @@ OAuth helps in that regard.
 The method with which frontend plugins request access to third party services is
 through [Utility APIs](../api/utility-apis.md) for each service provider. For a
 full list of providers, see the
-[Utility API References](../reference/utility-apis/README.md).
+[@backstage/core-plugin-api](../reference/core-plugin-api.md#variables)
+reference.
 
 ### Identity - WIP
 

docs/conf/reading.md

@@ -7,7 +7,7 @@ description: Documentation on Reading Backstage Configuration
 ## Config API
 
 There's a common configuration API for by both frontend and backend plugins. An
-API reference can be found [here](../reference/utility-apis/Config.md).
+API reference can be found [here](../reference/config.Config.md).
 
 The configuration API is tailored towards failing fast in case of missing or bad
 config. That's because configuration errors can always be considered programming
@@ -110,7 +110,7 @@ example `getString`. These will throw an error if there is no value available.
 
 ## Accessing ConfigApi in Frontend Plugins
 
-The [ConfigApi](../reference/utility-apis/Config.md) in the frontend is a
+The [ConfigApi](../reference/core-plugin-api.ConfigApi.md) in the frontend is a
 [UtilityApi](../api/utility-apis.md). It's accessible as usual via the
 `configApiRef` exported from `@backstage/core-plugin-api`:
 

mkdocs.yml

@@ -156,14 +156,9 @@ nav:
       - Design: 'dls/design.md'
       - Contributing to Storybook: 'dls/contributing-to-storybook.md'
       - Figma: 'dls/figma.md'
-  - API references:
-      - TypeScript API:
+  - API Reference:
+      - Guides:
           - Utility APIs: 'api/utility-apis.md'
-          - reference/utility-apis/README: 'reference/utility-apis/README.md'
-          - createPlugin: 'reference/createPlugin.md'
-          - createPlugin -feature flags: 'reference/createPlugin-feature-flags.md'
-      - Backend APIs:
-          - Backend: 'api/backend.md'
   - Tutorials:
       - Future developer journey: 'tutorials/journey.md'
       - Migrating away from @backstage/core: 'tutorials/migrating-away-from-core.md'