mail/exim: update 4.99.3 -> 4.99.5, fix security issues

PR: 297061
Approved-by: maintainer (implicit)
Security: EXIM-Security-2026-06-22.1 (GCVE-25-2026-07-45-1)

		EXIM-Security-2026-06-22.3 (GCVE-25-2026-07-45-3)
		EXIM-Security-2026-05-19.1 (CVE-2026-48840)

Changes: https://lists.exim.org/lurker/message/20260529.143857.4c75d7df.en.html

		https://lists.exim.org/lurker/message/20260722.140124.4feb2a88.en.html

MFH: 2026Q3