The already frosty relationship between Julia Roberts and her big brother, Eric, has hit an iceberg now that the 68-year-old “Dark Knight” actor is bashing his sister’s acting chops in his new memoir. RadarOnline.com can reveal just months after revealing in an interview Julia had ordered him to not talk about her in public, Eric admitted, “But I do!” While he apologized for a 2018 interview in which he claimed credit for Julia’s stardom – admitting he made it up – he slammed her performance in the 1989 movie Steel Magnolias, which earned Julia her first Academy Awards nod. “Julia was good in …