[llvm] [WebAssembly] Fix rethrow's index calculation (PR #114693)

[Derek Schuff via llvm-commits]

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@@ -180,11 +181,9 @@ let isTerminator = 1, hasSideEffects = 1, isBarrier = 1, hasCtrlDep = 1,
 // Rethrowing an exception: rethrow
 // The new exnref proposal also uses this instruction as an interim pseudo
 // instruction before we convert it to a THROW_REF.
+// $ehpad is the EH pad where the exception the rethrow has been caught.
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dschuff wrote:

```suggestion
// $ehpad is the EH pad where the exception to rethrow has been caught.
```

https://github.com/llvm/llvm-project/pull/114693