fix(docs): add usage deprecation

[bshaffer]

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[snippet-bot]

Here is the summary of changes.

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• tests/Unit/ProtoTests/Basic/out/samples/BasicClient/a_method.php:25, tag basic_generated_Basic_AMethod_sync
• tests/Unit/ProtoTests/Basic/out/samples/BasicClient/method_with_args.php:25, tag basic_generated_Basic_MethodWithArgs_sync

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