jest: make regex for tests stricter

Summary:
Updated the configuration for all projects on xplat/js to only consider tests that end with `-test.js`.

All tests were migrated in the previous diff of the stack.

Reviewed By: mjesun

Differential Revision: D13185676

fbshipit-source-id: baaba94fabc403acb30b0b5a0462788813d7a870

Author: rubennorte

package.json

@@ -30,6 +30,7 @@
     "moduleNameMapper": {
       "^React$": "<rootDir>/Libraries/react-native/React.js"
     },
+    "testRegex": "/__tests__/.*-test\\.js$",
     "testPathIgnorePatterns": [
       "Libraries/Renderer",
       "/node_modules/",