Enable --incompatible_disallow_dict_plus by default

Fixes #6461

RELNOTES: --incompatible_disallow_dict_plus is enabled by default
PiperOrigin-RevId: 234829823

src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java

diff --git a/src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java b/src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java
index 231480a..78b70e6 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java
@@ -258,7 +258,7 @@
 
   @Option(
       name = "incompatible_disallow_dict_plus",
-      defaultValue = "false",
+      defaultValue = "true",
       documentationCategory = OptionDocumentationCategory.STARLARK_SEMANTICS,
       effectTags = {OptionEffectTag.BUILD_FILE_SEMANTICS},
       metadataTags = {

src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java

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 f075118..fd40dd5 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
@@ -218,7 +218,7 @@
           .incompatibleDisableDeprecatedAttrParams(false)
           .incompatibleDisableObjcProviderResources(false)
           .incompatibleDisallowDataTransition(true)
-          .incompatibleDisallowDictPlus(false)
+          .incompatibleDisallowDictPlus(true)
           .incompatibleDisallowFileType(true)
           .incompatibleDisallowLegacyJavaProvider(false)
           .incompatibleDisallowLegacyJavaInfo(false)