chore(date-pickers): fix mock date in tests

[guidozoli]

Description

DatePicker, RangePicker. Fixed tests

[IMPORTANT] PR Checklist

• I am aware of standards and conventions adopted in this repository, defined in the CONTRIBUTING.md file

PR conventions

Please make sure your PR complies with the following rules before submitting it.

• PR title follows the <type>(<scope>): <subject> structure

• The PR has been labeled according to the type of changes (e.g. enhancement, new component, bug).

  NOTE
  Some labels are used to generate release note entries: you can find the complete mapping between PR labels and release note categories here.
  For a more detailed overview of PR labels, please refer to the dedicated CONTRIBUTING section.

Additional code checks

Based on your changes, some of these checks may not apply. Please make sure to check the relevant items in the list.

• Changes are covered by tests
• Changes to components are accessible and documented in the Storybook
• Typings have been updated
• New components are exported from the src/index.ts file
• New files include the Apache 2.0 License disclaimer
• The browser console does not contain errors