security/vuxml: update fetchmail CVE-2021-36386 vuln

this vuln was a reintroduction of CVE-2008-2711 which got fixed in
fetchmail 6.3.9, when 6.3.17 refactored code.

• restrict range (>= 6.3.9 < 6.3.17 unaffected)
• add reference to old CVE-2008-2711

URL: https://www.fetchmail.info/fetchmail-SA-2021-01.txt
Security: cbfd1874-efea-11eb-8fe9-036bd763ff35
Security: CVE-2021-36386
Security: CVE-2008-2711