Fix typo in operator file name

[RainbowMango]

Task description:
Fix the typo(mainfests.go --> manifests) in the following file name:

• https://github.com/karmada-io/karmada/blob/master/operator/pkg/controlplane/apiserver/mainfests.go
• https://github.com/karmada-io/karmada/blob/master/operator/pkg/controlplane/etcd/mainfests.go
• https://github.com/karmada-io/karmada/blob/master/operator/pkg/controlplane/metricsadapter/mainfests.go
• https://github.com/karmada-io/karmada/blob/master/operator/pkg/controlplane/search/mainfests.go
• https://github.com/karmada-io/karmada/blob/master/operator/pkg/controlplane/webhook/mainfests.go

Note: This task should wait for #5536 to avoid conflicts.

Solution:

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[husnialhamdani]

Hi @RainbowMango, I interested to work on this

[RainbowMango]

Sure, go for it.
/assign @husnialhamdani