docs: Update README.md

Author: Checho3388

README.md

@@ -44,7 +44,7 @@ query = """
 complexity = get_complexity(
     query=query, 
     schema=schema,
-    estimator=SimpleEstimator(complexity=1, multiplier=10)
+    estimator=SimpleEstimator(complexity=10)
 )
 if complexity > 10:
     raise Exception("Query is too complex")
@@ -73,7 +73,7 @@ it by another **constant** which is propagated along the depth of the query.
 from graphql_complexity import SimpleEstimator
 
 
-estimator = SimpleEstimator(complexity=2, multiplier=1)
+estimator = SimpleEstimator(complexity=2)
 ```
 
 Given the following GraphQL query:
@@ -150,13 +150,10 @@ from graphql_complexity import ComplexityEstimator
 
 
 class CustomEstimator(ComplexityEstimator):
-    def get_field_complexity(self, node, key, parent, path, ancestors) -> int:
+    def get_field_complexity(self, node, type_info, path) -> int:
         if node.name.value == "specificField":
             return 100
         return 1
-
-    def get_field_multiplier(self, node, key, parent, path, ancestors) -> int:
-        return 1
 ```