Breaking Change: Remove deprecated UseDeprecatedLegacyJsonFieldConflicts()

https://protobuf.dev/news/2025-09-19/#cpp-remove-apis

PiperOrigin-RevId: 853477445

Author: anandolee

python/google/protobuf/pyext/descriptor_pool.cc

@@ -148,8 +148,7 @@ static PyDescriptorPool* PyDescriptorPool_NewWithUnderlay(
 }
 
 static PyDescriptorPool* PyDescriptorPool_NewWithDatabase(
-    DescriptorDatabase* database,
-    bool use_deprecated_legacy_json_field_conflicts) {
+    DescriptorDatabase* database) {
   PyDescriptorPool* cpool = _CreateDescriptorPool();
   if (cpool == nullptr) {
     return nullptr;
@@ -164,11 +163,6 @@ static PyDescriptorPool* PyDescriptorPool_NewWithDatabase(
     pool = new DescriptorPool();
     cpool->is_mutable = true;
   }
-  if (use_deprecated_legacy_json_field_conflicts) {
-    PROTOBUF_IGNORE_DEPRECATION_START
-    pool->UseDeprecatedLegacyJsonFieldConflicts();
-    PROTOBUF_IGNORE_DEPRECATION_STOP
-  }
   cpool->pool = pool;
   cpool->is_owned = true;
 
@@ -188,7 +182,6 @@ static PyDescriptorPool* PyDescriptorPool_NewWithDatabase(
 // The public DescriptorPool constructor.
 static PyObject* New(PyTypeObject* type,
                      PyObject* args, PyObject* kwargs) {
-  int use_deprecated_legacy_json_field_conflicts = 0;
   static const char* kwlist[] = {"descriptor_db", nullptr};
   PyObject* py_database = nullptr;
   if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O",
@@ -200,7 +193,7 @@ static PyObject* New(PyTypeObject* type,
     database = new PyDescriptorDatabase(py_database);
   }
   return reinterpret_cast<PyObject*>(PyDescriptorPool_NewWithDatabase(
-      database, use_deprecated_legacy_json_field_conflicts));
+      database));
 }
 
 static void Dealloc(PyObject* pself) {

src/google/protobuf/descriptor.h

@@ -2583,12 +2583,6 @@ class PROTOBUF_EXPORT DescriptorPool {
   // Disallow [enforce_utf8 = false] in .proto files.
   void DisallowEnforceUtf8() { disallow_enforce_utf8_ = true; }
 
-  // Use the deprecated legacy behavior for handling JSON field name conflicts.
-  ABSL_DEPRECATED("Deprecated treatment of field name conflicts is enabled.")
-  void UseDeprecatedLegacyJsonFieldConflicts() {
-    deprecated_legacy_json_field_conflicts_ = true;
-  }
-
 
   // For internal use only:  Gets a non-const pointer to the generated pool.
   // This is called at static-initialization time only, so thread-safety is