finetune: Rename command name in README.md (#8343)

Rename an old command name "finetune" to "llama-finetune"
in README.md

Signed-off-by: Masanari Iida <standby24x7@gmail.com>

examples/finetune/README.md

@@ -87,4 +87,4 @@ The LORA rank can be configured for each model tensor type separately with these
 
 The LORA rank of 'norm' tensors should always be 1.
 
-To see all available options use `finetune --help`.
+To see all available options use `llama-finetune --help`.