fix(go): properties on interfaces should be uppercased

[DanielMSchmidt]

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I'm trying to adjust rosetta so that it aligns with what JSII is doing. I am seeing consistently lower-cased property / method names, where JSII would uppercase them. One example from the cdktf aws pre-built provider is this interface in TS and the coresponding go struct. Rosetta would lower-case the names the JSII puts in uppercase.