Rename schema imports to jsonSchema and remove stale changeset

Rename the JSON schema imports in kind definitions from `schema` to
`jsonSchema` to enable shorthand property syntax. Also remove the
stale scaffolder-backend changeset since that package no longer has
changes in this PR.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Fredrik Adelöw <freben@spotify.com>

plugins/scaffolder-common/src/catalogModel.ts

@@ -15,8 +15,8 @@
  */
 
 import { createCatalogModelLayer } from '@backstage/catalog-model/alpha';
-import { JsonObject } from '@backstage/types';
-import schema from './Template.v1beta3.schema.json';
+import type { JsonObject } from '@backstage/types';
+import jsonSchema from './Template.v1beta3.schema.json';
 
 /**
  * Extends the catalog model with the Template kind.
@@ -48,7 +48,7 @@ export const scaffolderCatalogModelLayer = createCatalogModelLayer({
             },
           ],
           schema: {
-            jsonSchema: schema as JsonObject,
+            jsonSchema: jsonSchema as JsonObject,
           },
         },
       ],