Remove the y24_052_enable_data_release_timing_validation feature flag

[KatyTaylor]

Changes proposed in this pull request

• Remove the y24_052_enable_data_release_timing_validation feature flag
• It was introduced in 'Y24-052 [BUG] Dropdown list dependencies', to turn the new server-side validation off until the existing data was fixed
• It can be removed after 'Y24-058 [BUG] Study data release information - data clean up' is done

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