PrimaryKeyRelatedField(read_only=True, pk_field=IntegerField()) have incorrect scheme

[MaHryCT3]

Describe the bug
I found a couple issues already solved related to this, but not found about pk_field. The problem is related to PrimaryKeyRelatedField(read_only=True). I try to add to this pk_field=IntegerField, but schema field=STR

To Reproduce

from drf_spectacular.utils import extend_schema
from rest_framework import serializers
from rest_framework.viewsets import ViewSet
from rest_framework.response import Response


class ResponseSerializer(serializers.Serializer):
    route = serializers.PrimaryKeyRelatedField(
        read_only=True,
        pk_field=serializers.IntegerField(),
    )


class AnalysisRouteSchemeViewSet(ViewSet):

    @extend_schema(
        responses=ResponseSerializer,
    )
    def list(self, *args, **kwargs):
        return Response()

Expected behavior
Schema type taken from pk_field if pk_field defined

Place in code: https://github.com/tfranzel/drf-spectacular/blob/master/drf_spectacular/openapi.py#L712