Update place holders from [PARAM_NAME] to <PARAM_NAME>

[gewenyu99]

What does this PR do?

When generating specs, we use x-example to populate examples in the generated code examples.
We used to use the format [PARAM NAME] because we had a specific PHTML restriction on <> type place holders.

Now we can switch to <> type tokens, so these placeholders will not be confused with arrays.

Test Plan

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• Have you read the Contributing Guidelines on issues?
• If the PR includes a change to an API's metadata (desc, label, params, etc.), does it also include updated API specs and example docs?