Fix ctrl+shift+p for PDF

Currentl we are intercepting ctrl+p on PDF to print, which is interfering
with ctrl+shift+p. There is no need to intercept either of these commands
anymore, the default handling should work correctly.

BUG=466600

Review URL: https://codereview.chromium.org/1031293004

Cr-Commit-Position: refs/heads/master@{#322328}

chrome/browser/resources/pdf/pdf.js

@@ -313,13 +313,6 @@ PDFViewer.prototype = {
           e.preventDefault();
         }
         return;
-      case 80:  // p key.
-        if (e.ctrlKey || e.metaKey) {
-          this.print_();
-          // Since we do the printing of the page.
-          e.preventDefault();
-        }
-        return;
       case 219:  // left bracket.
         if (e.ctrlKey)
           this.rotateCounterClockwise_();