Fixed number of LEDs in the "RGB Light" entity to 1

[ha-elguano]

Version: 25.7.18.2

What does this implement/fix?

1. Existing code has MSR-1 as having 3 LEDs in the strip (carryover from Air-1?). I just corrected this to 1.

2. Proposing a default rmt_symbols value of 48. This is not strictly needed, but helps anyone adding a second LED strip from having to extend the "RGB Light" entity. 48 is the only real choice due to ESP32-C3's limit of 92 tx symbols, assignable in 48-symbol chunks (so it might as well be a default, as adding another RMT LED would require that one to be 48 as well).

Types of changes

• Bugfix (fixed change that fixes an issue)
• New feature (thanks!)
• Breaking change (repair/feature that breaks existing functionality)
• Dependency Update - Does not publish
• Other - Does not publish
• Website of github readme file update - Does not publish
• Github workflows - Does not publish

Checklist / Checklijst:

• The code change has been tested and works locally
• The code change has not yet been tested

If user-visible functionality or configuration variables are added/modified:

• Added/updated documentation for the web page