Remove i966.scala test and corresponding code path

We can't compile this test with the 2.13 stdlib, and the only codepath
it's supposed to exerce is currently dead code, I assume that the raw
Array that showed up there was due to some bug that has since been
fixed.

Author: smarter

compiler/src/dotty/tools/dotc/core/TypeErasure.scala

@@ -435,7 +435,6 @@ class TypeErasure(isJava: Boolean, semiEraseVCs: Boolean, isConstructor: Boolean
       val sym = tp.symbol
       if (!sym.isClass) this(tp.translucentSuperType)
       else if (semiEraseVCs && isDerivedValueClass(sym)) eraseDerivedValueClassRef(tp)
-      else if (sym == defn.ArrayClass) apply(tp.appliedTo(TypeBounds.empty)) // i966 shows that we can hit a raw Array type.
       else if (defn.isSyntheticFunctionClass(sym)) defn.erasedFunctionType(sym)
       else eraseNormalClassRef(tp)
     case tp: AppliedType =>