Change `sh` alias back to `bash`

because this is the alias in highlight itself.

(see https://github.com/writeas/writefreely/pull/128#issuecomment-505766645)

templates/include/post-render.tmpl

@@ -22,7 +22,7 @@
       "hh"         : "cpp",
       "hxx"        : "cpp",
       "cxx"        : "cpp",
-      "sh"         : "shell"
+      "sh"         : "bash"
     };
     
     // Given a set of nodes, run highlighting on them