[Sync EN] filter/constants.xml: Mention the scientific notation for `float` (#5617)

[github-actions]

Commit: https://github.com/php/doc-en/commit/1c5ff30e9ae64bd4fd7ebbd0cccfb1e642e1b02c
PR: https://github.com/php/doc-en/pull/5617

Zu aktualisierende DE-Dateien

• reference/filter/constants.xml