fix: revert set up globalThis for jest tests

This reverts commit db212a4.
We no longer test in Node.js 10.x

Author: trivikr

jest.config.js

@@ -9,5 +9,4 @@ module.exports = {
   ],
   testPathIgnorePatterns: ["/node_modules/", "<rootDir>/clients/client-.*"],
   coveragePathIgnorePatterns: ["/node_modules/", "<rootDir>/clients/client-.*", "/__fixtures__/"],
-  setupFiles: ["<rootDir>/scripts/jest/setupGlobalThis.js"],
 };