fix typo in mappings.py

megatron/mpu/mappings.py

@@ -20,7 +20,7 @@ from .utils import split_tensor_along_last_dim
 
 
 def _reduce(input_):
-    """All-reduce the the input tensor across model parallel group."""
+    """All-reduce the input tensor across model parallel group."""
 
     # Bypass the function if we are using only 1 GPU.
     if get_tensor_model_parallel_world_size()==1: