doc(docs.mockFunctions): use SAME JS module system

[dancer1325]

Summary

• In Using a mock function, you can see that
  • in js title="forEach.test.js" , that require is used == CommonJS
  • in js title="forEach.js", that export is used == ES
• ⚠️That's why lot of pitfalls you will get, mixin them ⚠️
• Solution:
  • align to use CommonJS in both files defined

Test plan

• Create both 2 files
• Create the minimum set up to make jest work -- see gettingStarted --
• Run it to test
  

[linux-foundation-easycla]

• ✅login: dancer1325 / (e416d58)

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[dancer1325]

maybe @SimenB ?