schemas/gen: exclude harness-io/harness

[radeksimko]

This is in reaction to the following
https://github.com/hashicorp/terraform-ls/runs/5419512936?check_suite_focus=true#step:6:47

Error: Incompatible provider version

Provider registry.terraform.io/harness-io/harness v0.1.15 does not have a
package available for your current platform, linux_amd64.

Provider releases are separate from Terraform CLI releases, so not all
providers are available for all platforms. Other versions of this provider
may have different platforms supported.

[github-actions]

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