[doc] update markdown --stop-stage to --stop_stage (#1592)

Co-authored-by: zdb <[email protected]>

Author: DaobinZhu

docs/tutorial_aishell.md

@@ -14,19 +14,19 @@ The recipe is simple and we suggest you run each stage one by one manually and c
 
 ```
 cd example/aishell/s0
-bash run.sh --stage -1 --stop-stage -1
-bash run.sh --stage 0 --stop-stage 0
-bash run.sh --stage 1 --stop-stage 1
-bash run.sh --stage 2 --stop-stage 2
-bash run.sh --stage 3 --stop-stage 3
-bash run.sh --stage 4 --stop-stage 4
-bash run.sh --stage 5 --stop-stage 5
-bash run.sh --stage 6 --stop-stage 6
+bash run.sh --stage -1 --stop_stage -1
+bash run.sh --stage 0 --stop_stage 0
+bash run.sh --stage 1 --stop_stage 1
+bash run.sh --stage 2 --stop_stage 2
+bash run.sh --stage 3 --stop_stage 3
+bash run.sh --stage 4 --stop_stage 4
+bash run.sh --stage 5 --stop_stage 5
+bash run.sh --stage 6 --stop_stage 6
 ```
 
 You could also just run the whole script
 ```
-bash run.sh --stage -1 --stop-stage 6
+bash run.sh --stage -1 --stop_stage 6
 ```
 
 

docs/tutorial_librispeech.md

@@ -14,20 +14,20 @@ The recipe is simple and we suggest you run each stage one by one manually and c
 
 ```
 cd example/librispeech/s0
-bash run.sh --stage -1 --stop-stage -1
-bash run.sh --stage 0 --stop-stage 0
-bash run.sh --stage 1 --stop-stage 1
-bash run.sh --stage 2 --stop-stage 2
-bash run.sh --stage 3 --stop-stage 3
-bash run.sh --stage 4 --stop-stage 4
-bash run.sh --stage 5 --stop-stage 5
-bash run.sh --stage 6 --stop-stage 6
-bash run.sh --stage 7 --stop-stage 7
+bash run.sh --stage -1 --stop_stage -1
+bash run.sh --stage 0 --stop_stage 0
+bash run.sh --stage 1 --stop_stage 1
+bash run.sh --stage 2 --stop_stage 2
+bash run.sh --stage 3 --stop_stage 3
+bash run.sh --stage 4 --stop_stage 4
+bash run.sh --stage 5 --stop_stage 5
+bash run.sh --stage 6 --stop_stage 6
+bash run.sh --stage 7 --stop_stage 7
 ```
 
 You could also just run the whole script
 ```
-bash run.sh --stage -1 --stop-stage 7
+bash run.sh --stage -1 --stop_stage 7
 ```