Mark repository_rule implementation parameter as intentionally keyword-specifiable

Progress toward #5010.

RELNOTES: None.
PiperOrigin-RevId: 244211187
diff --git a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/repository/RepositoryModuleApi.java b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/repository/RepositoryModuleApi.java
index 588f9a2..2e138c8 100644
--- a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/repository/RepositoryModuleApi.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/repository/RepositoryModuleApi.java
@@ -40,7 +40,7 @@
         @Param(
             name = "implementation",
             type = BaseFunction.class,
-            legacyNamed = true,
+            named = true,
             doc =
                 "the function implementing this rule, has to have exactly one parameter: "
                     + "<code><a href=\"repository_ctx.html\">repository_ctx</a></code>. The function "