help request: cannot start prometheus input plugin

### Describe the issue

I'm trying to use prometheus input plugin with a very simple way taken from examples. Unfortunately logs of the fluent-bit pods contain the following error:
`
Input plugin 'prometheus_scrape' cannot be loaded
Error: Configuration file contains errors. Aborting
`
I cannot find a way to check the config and have no idea how to fix it, please help.

### How did you install fluent operator?

via one of the official way:
kubectl apply -f https://raw.githubusercontent.com/fluent/fluentbit-operator/master/manifests/setup/setup.yaml --server-side

### Additional context
`
apiVersion: fluentbit.fluent.io/v1alpha2
kind: FluentBit
metadata:
name: fluent-bit
namespace: fluent
labels:
app.kubernetes.io/name: fluent-bit
spec:
image: kubesphere/fluent-bit:v1.8.11
positionDB:
hostPath:
path: /var/lib/fluent-bit/
resources:
requests:
cpu: 10m
memory: 25Mi
limits:
cpu: 500m
memory: 200Mi
fluentBitConfigName: fluent-bit-only-config
tolerations:
- operator: Exists
---
apiVersion: fluentbit.fluent.io/v1alpha2
kind: ClusterFluentBitConfig
metadata:
name: fluent-bit-only-config
labels:
app.kubernetes.io/name: fluent-bit
spec:
service:
parsersFile: parsers.conf
inputSelector:
matchLabels:
fluentbit.fluent.io/enabled: "true"
fluentbit.fluent.io/mode: "fluentbit-only"
filterSelector:
matchLabels:
fluentbit.fluent.io/enabled: "true"
fluentbit.fluent.io/mode: "fluentbit-only"
outputSelector:
matchLabels:
fluentbit.fluent.io/enabled: "true"
fluentbit.fluent.io/mode: "fluentbit-only"
---
apiVersion: fluentbit.fluent.io/v1alpha2
kind: ClusterInput
metadata:
name: kubelet
labels:
fluentbit.fluent.io/enabled: "true"
fluentbit.fluent.io/mode: "fluentbit-only"
spec:
prometheusScrapeMetrics:
tag: cnpg
host: 172.16.0.172
port: 9187
metricsPath: /metrics
scrapeInterval: 10s
---
apiVersion: fluentbit.fluent.io/v1alpha2
kind: ClusterOutput
metadata:
name: stdout
labels:
fluentbit.fluent.io/enabled: "true"
fluentbit.fluent.io/mode: "fluentbit-only"
spec:
stdout: {}
`