Undocument flag_enabled() in repository rule

Set documented=false so that it doesn't show in documentation pages.

RELNOTES:none
PiperOrigin-RevId: 299881107
diff --git a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/repository/SkylarkRepositoryContextApi.java b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/repository/SkylarkRepositoryContextApi.java
index e0e1091..b9975e3 100644
--- a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/repository/SkylarkRepositoryContextApi.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/repository/SkylarkRepositoryContextApi.java
@@ -589,6 +589,7 @@
           "This method is present temporarily for a migration. It can be used only by a few "
               + "whitelisted bzl files embedded in Bazel.",
       useStarlarkThread = true,
+      documented = false,
       parameters = {
         @Param(name = "flag", type = String.class, doc = "Flag to get the value for."),
       })