Fix spaceholdings/nebula68b

[zvecr]

Description

Keyboard incorrectly contains nested build targets.

$ qmk lint -kb spaceholdings/nebula68b
Ψ Lint check passed!

$ qmk lint -kb spaceholdings/nebula68b/hs
☒ spaceholdings/nebula68b/hs: Invalid keyboard.json location detected: keyboards/spaceholdings/nebula68b/keyboard.json.
☒ spaceholdings/nebula68b/hs: Invalid keyboard.json location detected: keyboards/spaceholdings/nebula68b/keyboard.json.
☒ spaceholdings/nebula68b/hs: Errors found when generating info.json.
☒ spaceholdings/nebula68b/hs: Invalid keyboard.json location detected: keyboards/spaceholdings/nebula68b/keyboard.json.
☒ spaceholdings/nebula68b/hs: Invalid keyboard.json location detected: keyboards/spaceholdings/nebula68b/keyboard.json.
☒ Lint check failed for: spaceholdings/nebula68b/hs

With the enhanced linting it is now correctly flagging that its structure is wrong.

Content has been migrated to a new solder build target to avoid the above issues.

Types of Changes

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

Issues Fixed or Closed by This PR

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).