rgblight: Enable twinkle mode in rgblight

[yokada-code]

Description

rand() returns an integer type value which is usually a very large value compared with the threshold in the current lottery logic with uint8_t. Because of this, most of the lottery fails and no twinkle is observed on the keyboard.

Cherry-picked from the original qmk repository: 571a9794af0249ef23a0af2ed2ee64191299faa7

Types of Changes

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

Issues Fixed or Closed by This PR

• (none)

Checklist

• [x] My code follows the code style of this project: C, Python
• [x] 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.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] I have tested the changes and verified that they work and don't break anything (as well as I can manage).