Fix ForkedConvRepo add_injector signature

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "breakshaft"
-version = "0.1.6.post2"
+version = "0.1.6.post3"
 description = "Library for in-time codegen for type conversion"
 authors = [
     { name = "nikto_b", email = "niktob560@yandex.ru" }

src/breakshaft/convertor.py

@@ -194,9 +194,6 @@ class ForkedConvRepo(ConvRepo):
         self._convertor_set = fork_with
         self._base_repo = fork_from
 
-    def add_injector(self, func: Callable, rettype: Optional[type] = None):
-        self._convertor_set |= set(ConversionPoint.from_fn(func, rettype=rettype))
-
     @property
     def convertor_set(self):
         return self._base_repo.convertor_set | self._convertor_set