fix for wrong rule syntax. prop-types instead of react/prop-types in docs

Author: markus-willems

docs/rules/prop-types.md

@@ -102,7 +102,7 @@ This rule can take one argument to ignore some specific props during validation.
 
 ```
 ...
-"prop-types": [<enabled>, { ignore: <ignore>, customValidators: <customValidator> }]
+"react/prop-types": [<enabled>, { ignore: <ignore>, customValidators: <customValidator> }]
 ...
 ```