docs: resubmit pr17107 doc changes

credits: https://github.com/snitin315

Refs:
* eslint#17225
* eslint#17107

docs/src/extend/custom-rules.md

@@ -518,7 +518,7 @@ module.exports = {
 };
 ```
 
-**Deprecated:** The `context.getScope()` method is deprecated; make sure to use `context.sourceCode` property instead.
+**Deprecated:** The `context.getSourceCode()` method is deprecated; make sure to use `context.sourceCode` property instead.
 
 Once you have an instance of `SourceCode`, you can use the following methods on it to work with the code: