Revert opset 25 version bump (onnx#7441)

Fixes onnx#7439 
v1.20.0 is not introducing opset25

Signed-off-by: Ti-Tai Wang <titaiwang@microsoft.com>

Author: titaiwangms

onnx/defs/operator_sets.h

@@ -1396,17 +1396,6 @@ class OpSet_Onnx_ver24 {
   }
 };
 
-// Forward declarations for ai.onnx version 25
-
-// Iterate over schema from ai.onnx version 25
-class OpSet_Onnx_ver25 {
- public:
-  static void ForEachSchema(const std::function<void(OpSchema&&)>& fn) {
-    // TODO: Remove after introducing the first schema to opset 25
-    (void)fn;
-  }
-};
-
 inline void RegisterOnnxOperatorSetSchema() {
   RegisterOpSetSchema<OpSet_Onnx_ver1>();
   RegisterOpSetSchema<OpSet_Onnx_ver2>();
@@ -1432,7 +1421,6 @@ inline void RegisterOnnxOperatorSetSchema() {
   RegisterOpSetSchema<OpSet_Onnx_ver22>();
   RegisterOpSetSchema<OpSet_Onnx_ver23>();
   RegisterOpSetSchema<OpSet_Onnx_ver24>();
-  RegisterOpSetSchema<OpSet_Onnx_ver25>();
   // 0 means all versions of ONNX schema have been loaded
   OpSchemaRegistry::Instance()->SetLoadedSchemaVersion(0);
 }
@@ -1442,7 +1430,6 @@ inline void RegisterOnnxOperatorSetSchema(int target_version, bool fail_duplicat
   // These calls for schema registration here are required to be in descending order for this to work correctly
   //
   // Version-specific registration sees duplicate schema version request as error if fail_duplicate_schema
-  RegisterOpSetSchema<OpSet_Onnx_ver25>(target_version, fail_duplicate_schema);
   RegisterOpSetSchema<OpSet_Onnx_ver24>(target_version, fail_duplicate_schema);
   RegisterOpSetSchema<OpSet_Onnx_ver23>(target_version, fail_duplicate_schema);
   RegisterOpSetSchema<OpSet_Onnx_ver22>(target_version, fail_duplicate_schema);

onnx/defs/schema.h

@@ -908,7 +908,7 @@ class OpSchemaRegistry final : public ISchemaRegistry {
       // Increase the highest version when you make BC-breaking changes to the
       // operator schema on specific domain. Update the lowest version when it's
       // determined to remove too old version history.
-      map_[ONNX_DOMAIN] = std::make_pair(1, 25);
+      map_[ONNX_DOMAIN] = std::make_pair(1, 24);
       map_[AI_ONNX_ML_DOMAIN] = std::make_pair(1, 5);
       map_[AI_ONNX_TRAINING_DOMAIN] = std::make_pair(1, 1);
       // ONNX's preview domain contains operators subject to change, so