Fix spelling of "DNS over HTTPS" & "DNS over TLS"

Fix spelling of "DNS over HTTPS" & "DNS over TLS"

The terms "DNS over HTTPS" and "DNS over TLS" should be hyphenated when
they are used as adjectives and non-hyphenated otherwise.  Ensure all
occurrences of these terms in the source tree follow the above rule.
(CHANGES and release notes are intentionally left intact.)

Tweak a related ARM snippet, fixing a typo in the process.