Fix missing value in Zone11 message tag

[tgreenx]

Purpose

This PR fixes a missing value for message tag Z11_NO_SPF_NON_MAIL_DOMAIN in Zone11 test case.

How to test this PR

Tests should still pass.

Manual testing:

• Before this PR:

$ zonemaster-cli --show-testcase --level INFO --test zone11 --no-ipv6 fr

Seconds Level    Testcase       Message
======= ======== ============== =======
   0.00 INFO     Unspecified    Using version v8.1.0 of the Zonemaster engine.
   9.72 INFO     Zone11         No SPF policy was found for {domain}, which is a type of domain (root, TLD or under .ARPA) not expected to be used for email.

• After:

$ zonemaster-cli --show-testcase --level INFO --test zone11 --no-ipv6 fr

Seconds Level    Testcase       Message
======= ======== ============== =======
   0.00 INFO     Unspecified    Using version v8.1.0 of the Zonemaster engine.
   9.70 INFO     Zone11         No SPF policy was found for fr, which is a type of domain (root, TLD or under .ARPA) not expected to be used for email.

[tgreenx]

(Candidate for v2025.2.1)