Proposed changes

Since #3823, an inappropriate warning is printed
when a non-TLS connection is established to the local broker:

$ tedge mqtt sub te/#
2025-11-18T14:47:04.179834205Z  WARN MQTT: Connecting on port 1883 for insecure MQTT using a TLS connection

This warning is inappropriate because the connection is not established over TLS: neither a client certificate nor root certificates have been configured.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s. You can activate automatic signing by running just prepare-dev once)
• I ran just format as mentioned in CODING_GUIDELINES
• I used just check as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments