Added message to dependency_check function in line 23 of test/CMakeLists.txt file

Description

• Is this a new feature or a bug fix?: Bug fix
• Why these changes are necessary: Fix cmake configuring when AF_WITH_EXTERNAL_PACKAGES_ONLY enabled
• Potential impact on specific hardware, software or backends: None
• New functions and their functionality: None
• Can this PR be backported to older versions?: Yes
• Future changes not implemented in this PR: None

Fixes: #3563

Changes to Users

• No options added to the build
• No action required by the user

Checklist

• Rebased on latest master
• Code compiles
• Tests pass
• Functions added to unified API
• Functions documented