docs: remove unsafe eval section of security tutorial

[codebytere]

Description of Change

Closes #12929.

Removes Override and disable eval from our security tutorial.

/cc @MarshallOfSound

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• relevant documentation is changed or added
• PR title follows semantic commit guidelines

Release Notes

Notes: remove unsafe eval section of security tutorial, a good CSP is better and covers more cases

[release-clerk]

Release Notes Persisted

remove unsafe eval section of security tutorial, a good CSP is better and covers more cases

[trop]

I have automatically backported this PR to "4-0-x", please check out #15685

[brunolemos]

Electron 4.0.0 stills shows the warning about the unsafe-eval and send users to the docs and there's no info about this in the docs. What should users do exactly?

I overwrote the window.eval like old docs mentioned but I still get the warning. If I run window.eval() on console.log it was overwritten correctly.

[nornagon]

We should remove the warning from the code.

[nornagon]

... Actually, I think you're confusing the recommendation to set the unsafe-eval CSP with the recommend to disable the eval function by overriding it. The latter has never had a warning message associated with it in the renderer.