Correct position of @Nullable annotation: the returned AutoValue.Builder is never null, but the parameter toolchainContextKey might be.

PiperOrigin-RevId: 375143159
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/Dependency.java b/src/main/java/com/google/devtools/build/lib/analysis/Dependency.java
index 0b07692..936c47f 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/Dependency.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/Dependency.java
@@ -73,8 +73,8 @@
      * Sets the {@link ToolchainContextKey} that this dependency should use for toolchain
      * resolution.
      */
-    @Nullable
-    public abstract Builder setToolchainContextKey(ToolchainContextKey toolchainContextKey);
+    public abstract Builder setToolchainContextKey(
+        @Nullable ToolchainContextKey toolchainContextKey);
 
     // Not public.
     abstract Dependency autoBuild();