The default value of the required form option has been changed to false

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | a bit :)
| BC breaks?    | no
| Deprecations? | no
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

This feature will be introduce into SF 2.6. With this PR we could clean all the form and remove this option because we don't use html5 validation.
Too many lines...