test: Update jest.config.js to resolve warnings

[jleverenz]

Running (p)npm test logs these warnings:

ts-jest[ts-jest-transformer] (WARN) Define `ts-jest` config under `globals` is deprecated. Please do
transform: {
    <transform_regex>: ['ts-jest', { /* ts-jest config goes here in Jest */ }],
},
ts-jest[backports] (WARN) "[jest-config].globals.ts-jest.tsConfig" is deprecated, use "[jest-config].globals.ts-jest.tsconfig" instead.
ts-jest[backports] (WARN) Your Jest configuration is outdated. Use the CLI to help migrating it: ts-jest config:migrate <config-file>.

This PR makes the recommended changes and resolves the warnings.