mosquitto: Bump version to 2.0.12 for CVE fix

In version 2.0.11 a potential security bug (CVE-2021-34431) was fixed.

Reports:
https://nvd.nist.gov/vuln/detail/CVE-2021-34431
https://bugs.eclipse.org/bugs/show_bug.cgi?id=573191

Fix:
https://github.com/eclipse/mosquitto/commit/42163634c72d41a1f12d299f54e00adf14520eb2



Updating to the latest stable update 2.0.12 here for our reciep to
collect all the fixes. The notice.html file got renamed to NOTICE.md,
adjust accordingly.

Signed-off-by: Stefan Schmidt <stefan.schmidt@huawei.com>