Enable StrictMode everywhere in spec/dummy

[alexeyr-ci1]

See https://reactjs.org/docs/strict-mode.html. This should help detect more bugs in RoR.

[justin808]

@alexeyr-ci1 SGTM

[alexeyr-ci1]

@justin808 After #1463 to avoid doing the work twice, StrictMode added some more restrictions in React 18.

[ahangarha]

... StrictMode added some more restrictions in React 18.

In bad way? Anything particular apart from twice rendering which is deliberate?

May you please elaborate on this? @alexeyr-ci1

[alexeyr-ci1]

In bad way? Anything particular apart from twice rendering which is deliberate?

No, in a good way which catches more errors, which is what we want StrictMode for.