Fix use of //wrlib:error_code in BUILD definition.

bazel/wrlib/BUILD.bazel

@@ -4,7 +4,6 @@ rust_library(
     name = "error_code",
     srcs = ["error_code.rs"],
     edition = "2021",
-    visibility = ["//visibility:public"],
 )
 
 cc_test(
@@ -63,6 +62,7 @@ cc_library(
         "xutil.h",
     ],
     deps = [
+        ":error_code",
         "//config",
         "@ImageMagick//:lib",
         "@MagickWand//:lib",