js02: tests: add callbacks to prototype method calls

[danielthalhuber]

• Calling Array.prototype methods like map, forEach, filter, and find without a callback throws a TypeError
• The tests for challenges 8 and 10 call the prototype methods cMap and cFilter without callbacks (when testing with empty arrays)
• When there are no callbacks, any solutions that faithfully replicate these prototype methods (throw TypeErrors for missing callbacks) will fail the tests
• This commit adds callbacks to these method calls
• Adding the callbacks will not affect solutions that do not throw TypeErrors for missing callbacks

[songz]

thanks!