Fix M2M100 positional embedding creation for ONNX (#21328)

* Fix M2M100 positional embedding creation for ONNX

* Restore READMEs

* Trigger CI

src/transformers/models/m2m_100/modeling_m2m_100.py

@@ -172,7 +172,7 @@ class M2M100SinusoidalPositionalEmbedding(nn.Module):
         if max_pos > self.weights.size(0):
             self.make_weights(max_pos + self.offset, self.embedding_dim, self.padding_idx)
 
-        return self.weights.index_select(0, position_ids.view(-1)).view(bsz, seq_len, -1).detach()
+        return self.weights.index_select(0, position_ids.view(-1)).view(bsz, seq_len, self.weights.shape[-1]).detach()
 
     def create_position_ids_from_inputs_embeds(self, inputs_embeds, past_key_values_length):
         """

src/transformers/models/xglm/modeling_xglm.py

@@ -214,7 +214,7 @@ class XGLMSinusoidalPositionalEmbedding(nn.Module):
         if max_pos > self.weights.size(0):
             self.make_weights(max_pos + self.offset, self.embedding_dim, self.padding_idx)
 
-        return self.weights.index_select(0, position_ids.view(-1)).view(bsz, seq_len, -1).detach()
+        return self.weights.index_select(0, position_ids.view(-1)).view(bsz, seq_len, self.weights.shape[-1]).detach()
 
     def create_position_ids_from_inputs_embeds(self, inputs_embeds, past_key_values_length):
         """