feature #13407 [Form] Remove deprecated setDefaultOptions and OptionsResolverInterface (peterrehm)

This PR was merged into the 3.0-dev branch.

Discussion
----------

[Form] Remove deprecated setDefaultOptions and OptionsResolverInterface

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | symfony/symfony-docs#4786
| Related        | #12891

Commits
-------

9b9158b Remove the deprecated OptionsResolverInterface
6026781 Removed deprecated setDefaultOptions methods

Author: fabpot

OptionsResolver.php

@@ -24,7 +24,7 @@
  * @author Bernhard Schussek <bschussek@gmail.com>
  * @author Tobias Schultze <http://tobion.de>
  */
-class OptionsResolver implements Options, OptionsResolverInterface
+class OptionsResolver implements Options
 {
     /**
      * The fully qualified name of the {@link Options} interface.