Enable incompatible_disallow_load_labels_to_cross_package_boundaries by default

Fixes https://github.com/bazelbuild/bazel/issues/6408

Tested: https://buildkite.com/bazel/bazelisk-plus-incompatible-flags/builds/52

RELNOTES: `--incompatible_disallow_load_labels_to_cross_package_boundaries` is enabled by default
PiperOrigin-RevId: 240347889
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java b/src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java
index 9e54d4c..c60216d 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java
@@ -219,7 +219,7 @@
           .incompatibleDisallowFileType(true)
           .incompatibleDisallowLegacyJavaProvider(false)
           .incompatibleDisallowLegacyJavaInfo(false)
-          .incompatibleDisallowLoadLabelsToCrossPackageBoundaries(false)
+          .incompatibleDisallowLoadLabelsToCrossPackageBoundaries(true)
           .incompatibleDisallowNativeInBuildFile(false)
           .incompatibleDisallowOldStyleArgsAdd(true)
           .incompatibleDisallowStructProviderSyntax(false)