Docs: use correct rule name of 'v-on-function-call' in options example (#825)

Author: romansp

docs/rules/v-on-function-call.md

@@ -32,7 +32,7 @@ description: enforce or forbid parentheses after method calls without arguments
 Default is set to `never`.
 
 ```
-'vue/v-on-parens': [2, 'always'|'never']
+'vue/v-on-function-call': [2, 'always'|'never']
 ```
 
 ### `"always"` - Always use parentheses in `v-on` directives