Update slides/list.json

2020/2020-02-15_gnuLinuxCourse/slides/list.json

 [
-    { "filename": "index.md" },
+    { "filename" : "index.md" },
     { "filename" : "intro_first.md"},
     { "filename" : "intro_beforewebegin.md"},
     { "filename" : "intro_aim.md"},
-    { "filename": "overview.md" },
-    { "filename": "shell_intro.md" }
+    { "filename" : "ssh_intro.md"},
+    { "filename" : "ssh_intro_2.md"},
+    { "filename" : "ssh_intro_3.md"}
 ]