Remove wasi metadata (#3467)

## Motivation and Context
- Avoid getting a warning on every build
- Cargo will only allow one `0.12.0` to be published so this metadata
doesn't impact anything. A comment was added to clarify.

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Co-authored-by: ysaito1001 <awsaito@amazon.com>

rust-runtime/aws-smithy-wasm/Cargo.toml

@@ -19,7 +19,7 @@ http = "1.0.0"
 tracing = "0.1.40"
 # Note the wasi crate will only build for target wasm32-wasi, but having a target
 # statement here breaks some of the CI tests, so we leave it with the rest of the deps
-wasi = "0.12.0+wasi-0.2.0"
+wasi = "0.12.0" # This is build on wasi-0.2.0
 
 [package.metadata.docs.rs]
 all-features = true