fix: mssql - make instance_server_ca_cert output sensitive

[VladStarr]

Changed the mssql module output instance_server_ca_cert to be marked as sensitive.
This change should fix the following error:

│ Error: Output refers to sensitive values
│ 
│   on outputs.tf line 48:
│   48: output "instance_server_ca_cert" {
│ 
│ To reduce the risk of accidentally exporting sensitive data that was
│ intended to be only internal, Terraform requires that any root module
│ output containing sensitive data be explicitly marked as sensitive, to
│ confirm your intent.
│ 
│ If you do intend to export this data, annotate the output value as
│ sensitive by adding the following argument:
│     sensitive = true

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[imrannayer]

/gcbrun