js-test-runner: Add WorDBless dir to jest collectCoverageFrom (#22472)

The coverage report started taking an extra 10 minutes after
packages/my-jetpack added JS tests because it was reporting coverage for
all of WordPress that was brought in via WorDBless. Exclude that by
default.

Also exclude the `jetpack_vendor/` directory from
packages/composer-plugin for good measure.

tools/js-test-runner/jest-config/default.config.js

@@ -32,6 +32,8 @@ const defaultConfig = {
 		'**/*.{js,jsx}',
 		'!**/node_modules/**',
 		'!**/vendor/**',
+		'!**/jetpack_vendor/**',
+		'!**/wordpress/**', // WorDBless.
 		'!**/__tests__/**',
 		'!**/coverage/**',
 		'!test-main.{js,jsx}',