remove application/pdf->pdf transform in javascript

We have the old transforms because they were added before we realized it was a bad idea. We should not add new ones.

IPython/html/static/notebook/js/outputarea.js

@@ -819,7 +819,6 b' var IPython = (function (IPython) {'
         "image/svg+xml" : "svg",
         "image/png" : "png",
         "image/jpeg" : "jpeg",
-        "application/pdf" : "pdf",
         "text/latex" : "latex",
         "application/json" : "json",
         "application/javascript" : "javascript",
@@ -831,7 +830,6 b' var IPython = (function (IPython) {'
         "svg" : "image/svg+xml",
         "png" : "image/png",
         "jpeg" : "image/jpeg",
-        "pdf" : "application/pdf",
         "latex" : "text/latex",
         "json" : "application/json",
         "javascript" : "application/javascript",