Removed parser support for legacy syntax

Note that this was not included in GraphQL-core anyway,
so we just do some minor clean-up.

Replicates graphql/graphql-js@0d2bd54

Author: Cito

src/graphql/language/parser.py

@@ -658,10 +658,11 @@ def parse_object_type_definition(self) -> ObjectTypeDefinitionNode:
 
     def parse_implements_interfaces(self) -> List[NamedTypeNode]:
         """ImplementsInterfaces"""
-        if not self.expect_optional_keyword("implements"):
-            return []
-
-        return self.delimited_many(TokenKind.AMP, self.parse_named_type)
+        return (
+            self.delimited_many(TokenKind.AMP, self.parse_named_type)
+            if self.expect_optional_keyword("implements")
+            else []
+        )
 
     def parse_fields_definition(self) -> List[FieldDefinitionNode]:
         """FieldsDefinition: {FieldDefinition+}"""

tests/language/test_schema_parser.py

@@ -792,13 +792,3 @@ def directive_with_incorrect_locations():
 
     def parses_kitchen_sink_schema(kitchen_sink_sdl):  # noqa: F811
         assert parse(kitchen_sink_sdl)
-
-    def disallow_legacy_sdl_empty_fields_supports_type_with_empty_fields():
-        assert_syntax_error("type Hello { }", "Expected Name, found '}'.", (1, 14))
-
-    def disallow_legacy_sdl_implements_interfaces():
-        assert_syntax_error(
-            "type Hello implements Wo rld { field: String }",
-            "Unexpected Name 'rld'.",
-            (1, 26),
-        )