Update Skylark Readability Guidelines.
RELNOTES: None.
@@ -370,7 +370,7 @@ copying.
Providers can be declared using the [provider()](lib/globals.html#provider) function:
```python
-TransitiveDataInfo = provider()
+TransitiveDataInfo = provider(fields=["value"])
```
Rule implementation function can then construct and return provider instances:
