Update description of kubeconfig specific flag

[somtochiama]

The --insecure-skip-tls-verify, --certificate-authority, client-key and client-certificate are kubeconfig flags that are used when connecting to the Kubernetes API Server. The generic description sometimes makes users assume that this is for something else e.g see comment

Though I have the option --insecure-skip-tls-verify , still getting certifcate error.

This pull request updates the description to be clear about which server it is used for.
Before

--insecure-skip-tls-verify               If true, the server's certificate will not be checked for validity. This will make your HTTPS connections insecure
--certificate-authority string           Path to a cert file for the certificate authority
--client-certificate string              Path to a client certificate file for TLS
--client-key string                      Path to a client key file for TLS

After

--insecure-skip-tls-verify       If true, the Kubernetes API server's certificate will not be checked for validity. This will make your HTTPS connections insecure
--certificate-authority string   Path to a cert file for the certificate authority to authenticate Kubernetes API
--client-certificate string      Path to a client certificate file for TLS authentication to Kubernetes API
--client-key string              Path to a client key file for TLS authentication to Kubernetes API

[stefanprodan]

I propose we do the same for:

      --certificate-authority string   Path to a cert file for the certificate authority
      --client-certificate string      Path to a client certificate file for TLS
      --client-key string              Path to a client key file for TLS

[darkowlzz]

LGTM!

[fluxcdbot]

Successfully created backport PR for release/v2.1.x:

• [release/v2.1.x] Update description of kubeconfig specific flag #4250