test(backstage-plugin): Fix linting test files

Move test setup files out of source folder to avoid needing dependencies instead of dev dependencies
when compiling typescript.

Addresses #71

backstage-plugin/plugins/open-dora/package.json

@@ -72,7 +72,7 @@
       ]
     },
     "setupFiles": [
-      "./jest.polyfills.js"
+      "../testing/jest.polyfills.js"
     ]
   }
 }

backstage-plugin/plugins/open-dora/src/setupTests.ts

@@ -1,7 +1,7 @@
 import '@testing-library/jest-dom';
 import 'cross-fetch/polyfill';
 import { setupServer } from 'msw/node';
-import { handlers } from './mswHandlers';
+import { handlers } from '../testing/mswHandlers';
 
 export const server = setupServer(...handlers);