chore(node): removing our dependency on oas (#1054)

## 🧰 Changes

~~I don't totally understand why we're loading `oas` in for types on the
`getGroupIdByOperation` method that by all accounts seems to be unused,
but because the version of `oas` we are using is pretty old I'm
upgrading it.~~

Because `oas` is currently being used solely for
`getGroupIdByOperation`, a method that is not being used anywhere, I am
removing `getGroupIdByOperation` and our `oas` dependency.

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Co-authored-by: Kanad Gupta <[email protected]>