Change the visibility of stablehlo_portable_api

PiperOrigin-RevId: 781682250

Author: tensorflower-gardener

stablehlo/BUILD

@@ -1261,6 +1261,9 @@ cc_library(
  "stablehlo/api/PortableApi.h",
  ],
  includes = ["."],
+ visibility = [
+ "//learning/brain/mlir:stablehlo_friends",
+ ],
  deps = [
  ":register",
  ":stablehlo_serialization",