feat: Set `vpn_connection_customer_gateway_configuration` output to `sensitive = true`

[stefan-matic]

Description

When creating the VPN gateway the output fails because the vpn_connection_customer_gateway_configuration has sensitive values.

│ Error: Output refers to sensitive values
│ 
│   on outputs.tf line 81:
│   81: output "vpn_connection_customer_gateway_configuration" {
│ 
│ 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

Motivation and Context

In order for the apply to go through fully, I've set the output value to be sensitive.

Existing issue that mentions several PRs that already fixed the same problem: fixes #80

Breaking Changes

No breaking changes.

How Has This Been Tested?

• [n/a] I have updated at least one of the examples/* to demonstrate and validate my change(s)
• [✓] I have tested and validated these changes using one or more of the provided examples/* projects
• [✓] I have executed pre-commit run -a on my pull request

[stefan-matic]

Hello @bryantbiggs, can you let me know your thoughts on this? Do we just set the output to sensitive or did you have something else in mind?

[antonbabenko]

This PR is included in version 3.2.0 :tada:

[github-actions[bot]]

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