NEWS: add release notes for Turris OS 5.1.8

By fixing logging of dnsmasq, it means that in syslog it shows [1]:
Jan 23 11:56:47 turris dnsmasq[6233]: failed to send packet: Network unreachable
Jan 23 11:56:47 turris dnsmasq[6233]: failed to send packet: Network unreachable
Jan 23 11:56:48 turris dnsmasq[6233]: failed to send packet: Network unreachable

[1] https://forum.turris.cz/t/security-advisory-2021-01-19-1-dnsmasq-multiple-vulnerabilities/14666/5?u=pepe

NEWS

+5.1.8
+-----
+
+* Minor fixes in logging of dnsmasq
+
 5.1.7
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