Instruct metadata action to not use 'latest' tag

[kad-korpem]

Description

Between release 8.4.0-4 and 8.4.1, the docker/metadata-action seems to suddenly add latest to the list of tags. This is now explicitly turned off.

Type of change

• Configuration change

Checklist:

• I've double-checked the code in this PR myself
• I've left the code better than before (boy scout rule)
• The code is readable, comments are added that explain hard or non-obvious parts.
• I've expanded/improved the (unit) tests, when applicable
• I've run (unit) tests that prove my solution works
• There's no sensitive information like credentials in my PR