Terraform style guidance showcases multiple comment styles

### Description

Many languages support multiple commenting styles, but as a matter of style guide preference choose a single commenting style. Let's make the style guide consistent on comments in terraform example code. We might also consider having a commenting syntax guideline.

Using `# per line`: https://googlecloudplatform.github.io/samples-style-guide/#result
Using `/* .. */` style: https://googlecloudplatform.github.io/samples-style-guide/#description
Using `/* .. */` with `* per line`: https://googlecloudplatform.github.io/samples-style-guide/#minimal-arguments

### Impact

Code style consistency, low work impact.