EZP-30985: Removed deprecated choices_as_values Symfony form option

[emodric]

Question	Answer
JIRA issue	EZP-30985
Target version	eZ Platform 2.5.x

The choices_as_values Symfony form option has been deprecated since Symfony 3.1.

Ref: https://symfony.com/doc/3.4/reference/forms/types/choice.html#choices-as-values

QA

• Sanity checks in AdminUI for the following Field Types:

  • Author,
  • Country,
  • Date,
  • DateTime,
  • Media (Image, BinaryFile).

• Sanity check for creating Content Type with randomly choosen Field Types.

  • Adding Field Type,
  • Updating Field Type,
  • Choosing sort Field Type,
  • Choosing sort order,
  • Setting Field Group,
  • Country FT: default values,
  • Selection FT: default values,
  • Roles: adding/updating of policies,
  • Policies: Limitations chosen from a list (Language, ContentType, etc.)
  • Link manager: status filtering.

[alongosz]

@webhdx @ViniTou @mikadamczyk @Nattfarinn since this applies to v2.5.x, please let me know if you think we need extra QA here (according to the Sf doc this change should have no effect, so I'm leaning towards merging this).