fixed small typo in Native Stack Navigator (#1104)

an extra ' was placed in headerBlurEffect

Author: andre-paulo98

versioned_docs/version-6.x/native-stack-navigator.md

@@ -181,7 +181,7 @@ Supported values:
 - `systemThinMaterialDark`
 - `systemMaterialDark`
 - `systemThickMaterialDark`
-- `systemChromeMaterialDark'`
+- `systemChromeMaterialDark`
 
 Only supported on iOS.