fix: Fix startup sound for Preonic (#25132)

[PeterFalken]

Description

Added AUDIO_INIT_DELAY to config.h to resolve. Based on conversation for [Bug] #8825.
A similar fix was applied to Planck variant on #24893.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• fixes [Bug] No startup sound on Preonic. #25132

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).