docs/provider: Bulk update hcl code block language to terraform

[bflad]

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Reference: #15842
Reference: #17810

This is a simple find-replace of triple backtick hcl with triple backtick terraform. This will be automatically covered by tfproviderdocs checking in the future when -enable-contents-check is turned on in GitHub Actions (and other potential Markdown linting).

Previously (example reports):

	* website/docs/r/ami.html.markdown: error checking file contents: example section code block language (hcl) should be: ```terraform
	* website/docs/r/ami_copy.html.markdown: error checking file contents: example section code block language (hcl) should be: ```terraform
	* website/docs/r/ami_from_instance.html.markdown: error checking file contents: example section code block language (hcl) should be: ```terraform
	* website/docs/r/ami_launch_permission.html.markdown: error checking file contents: example section code block language (hcl) should be: ```terraform
	* website/docs/r/api_gateway_account.html.markdown: error checking file contents: example section code block language (hcl) should be: ```terraform
	* website/docs/r/api_gateway_api_key.html.markdown: error checking file contents: example section code block language (hcl) should be: ```terraform
	* website/docs/r/api_gateway_authorizer.html.markdown: error checking file contents: example section code block language (hcl) should be: ```terraform
...

Output from acceptance testing: N/A (documentation)

[breathingdust]

LGTM 🚀 🚀 (aside from merge conflicts)

[ghost]

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