[Form] Remove timezone options from DateType and TimeType

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #12239
| License       | MIT
| Doc PR        | https://github.com/symfony/symfony-docs/pull/4417

replaces #12380
This must be moved to the proper section (2.6 or 2.7).