[Form] max option of Length & Range Constraint

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11527
| License       | MIT
| Doc PR        | 

Extended option "pattern" because  "max_length"  has been marked as deprecated since 2.5
Could you replace the dot by a "\d"?