[Sync EN] PHP 8.4: Document some changes to ext/date (#4064)

Commit: `https://github.com/php/doc-en/commit/9eb962113cadccc164d196003062ff5d893de3a5`
PR: `https://github.com/php/doc-en/pull/4064`

**Zu aktualisierende DE-Dateien**
- `reference/datetime/dateinterval/createfromdatestring.xml`
- `reference/datetime/dateperiod/construct.xml`
- `reference/datetime/datetime/modify.xml`
- `reference/datetime/datetimeimmutable/modify.xml`
