Update the help text for " --ca-certificate" flag in tanzu config cert commands

[prkalle]

Bug description
Currently the help text for "--ca-certficate" has the below help text

❯ tanzu config cert add -h
Add a certificate configuration for a host

Usage:
tanzu config cert add [flags]

Examples:

    # Add CA certificate for a host
    tanzu config cert add --host test.vmware.com --ca-certificate path/to/ca/ert

    # Add CA certificate for a host:port
    tanzu config cert add --host test.vmware.com:8443 --ca-certificate path/to/ca/ert

    # Set to skip verifying the certificate while interacting with host
    tanzu config cert add --host test.vmware.com  --skip-cert-verify true

    # Set to allow insecure (http) connection while interacting with host
    tanzu config cert add --host test.vmware.com  --insecure true

Flags:
      --ca-certificate string     path to the public certificate
  -h, --help                      help for add
      --host string               host or host:port
      --insecure string           allow the use of http when interacting with the host (default "false")
      --skip-cert-verify string   skip server's TLS certificate verification (default "false")

Expected behavior

Remove the word "public" in the help text. It should be "path to CA certificate"

Steps to reproduce the bug / Relevant debug output

Output of tanzu version

v0.90.0
Environment where the bug was observed (cloud, OS, etc)