fix documentation in Consul_certificate_authority examples

[sosasanti]

I corrected a documentation error in the consul_certificate_authority resource. The example now correctly uses the jsonencode function instead of jsondecode.

• [x] Solved issue GH-405

Updated Documentation:

#Using the built-in CA with specific TTL
resource "consul_certificate_authority" "connect" {
  connect_provider = "consul"

  config_json = jsonencode({
    LeafCertTTL         = "24h"
    RotationPeriod      = "2160h"
    IntermediateCertTTL = "8760h"
  })
}

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