Fix a typo (#10700)

Author: laurit

docs/contributing/style-guideline.md

@@ -64,7 +64,7 @@ rough guideline of what are commonly accepted static imports:
 - Collections helpers (such as `singletonList()` and `Collectors.toList()`)
 - ByteBuddy `ElementMatchers` (for building instrumentation modules)
 - Immutable constants (where clearly named)
-- Singleton instances (especially where clearly named an hopefully immutable)
+- Singleton instances (especially where clearly named and hopefully immutable)
 - `tracer()` methods that expose tracer singleton instances
 
 ## Ordering of class contents