message: Fix internal attribute name used by grappler arithmetic optimizer (NFC)
  Attributes are supposed to match the regex "[a-z][a-z0-9_]+" according to
  the documentation in op_def.proto
diff: @@ -62,9 +62,9 @@ namespace {
  // Mark nodes created or optimized by a stage with a tag.
  constexpr char kAddOpsRewriteTag[] =
  - "_grappler:ArithmeticOptimizer:AddOpsRewriteStage";
  + "_grappler_ArithmeticOptimizer_AddOpsRewriteStage";
  constexpr char kMinimizeBroadcastsTag[] =
  - "_grappler:ArithmeticOptimizer:MinimizeBroadcasts";
  + "_grappler_ArithmeticOptimizer_MinimizeBroadcasts";
  // Extract values from a Const op to `values`. Returns true if succeeds.
  template <typename T>
  