fix typo in ppc target

Author: adamrk

arch/powerpc/rust/target.json

@@ -1,6 +1,5 @@
 {
   "arch": "powerpc64",
-  "code-mode": "kernel",
   "cpu": "ppc64le",
   "data-layout": "e-m:e-i64:64-n32:64",
   "env": "gnu",
@@ -27,4 +26,4 @@
   "target-mcount": "_mcount",
   "target-endian": "little",
   "target-pointer-width": "64"
-}
+}