plugins should not depend on core-api

contrib/docs/tutorials/quickstart-app-plugin/ExampleComponent.md

@@ -14,8 +14,8 @@ import {
   HeaderLabel,
   SupportButton,
   identityApiRef,
+  useApi,
 } from '@backstage/core';
-import { useApi } from '@backstage/core-api';
 import ExampleFetchComponent from '../ExampleFetchComponent';
 
 const ExampleComponent = () => {

contrib/docs/tutorials/quickstart-app-plugin/ExampleFetchComponent.md

@@ -11,8 +11,8 @@ import {
   TableColumn,
   Progress,
   githubAuthApiRef,
+  useApi,
 } from '@backstage/core';
-import { useApi } from '@backstage/core-api';
 import { graphql } from '@octokit/graphql';
 
 const query = `{