Remove ggml submodule in favor of llama.cpp

.gitmodules

@@ -1,6 +1,3 @@
-[submodule "ggml"]
-	path = ggml
-	url = https://github.com/manyoso/ggml.git
 [submodule "llama.cpp"]
 	path = llama.cpp
 	url = https://github.com/manyoso/llama.cpp.git