rules/sdk: G703 errors not propagated should obey hash.Hash.Write not returning an error

[odeke-em]

I've seen this error

[/go/src/github.com/cosmos/cosmos-sdk/crypto/hd/hdpath.go:269] - G703 (CWE-): Returned error is not propagated up the stack. (Confidence: HIGH, Severity: LOW)
    268: 	// sha512 does not err
  > 269: 	_, _ = mac.Write(data)
    270:

but really if we examine the signature per https://pkg.go.dev/hash#Hash we can see

We should check that the writer was of the type hash.Hash and ignore such reports.