Update submodule link to reflect https style (#981)

Signed-off-by: raviguptaamd <ravi.gupta@amd.com>

Author: raviguptaamd

.gitmodules

@@ -1,3 +1,3 @@
 [submodule "training/DeepSpeed-Domino/Megatron-LM"]
 	path = training/DeepSpeed-Domino/Megatron-LM
-	url = git@github.com:NVIDIA/Megatron-LM.git
+	url = https://github.com/NVIDIA/Megatron-LM.git