docs: Fix a few typos

[timgates42]

There are small typos in:

• CVE-2020-28018/exim-4.92/src/child.c
• CVE-2020-28018/exim-4.92/src/host.c
• CVE-2020-28018/exim-4.92/src/malware.c
• CVE-2020-9273/proftpd-1.3.7rc2/contrib/mod_tls.c
• CVE-2020-9273/proftpd-1.3.7rc2/src/str.c

Fixes:

• Should read renegotiations rather than reneogtiations.
• Should read idempotent rather than ideempotent.
• Should read dnssec rather than dnsssec.
• Should read circuit rather than ciruit.
• Should read account rather than acount.

Semi-automated pull request generated by https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md