remove legacy vendor prefixes from pdf css

css/print/pdf.css

@@ -72,15 +72,8 @@ ul, ol, div, p {
 	overflow: visible;
 	display: block;
 
-	-webkit-perspective: none;
-	   -moz-perspective: none;
-	    -ms-perspective: none;
-	        perspective: none;
-
-	-webkit-perspective-origin: 50% 50%; /* there isn't a none/auto value but 50-50 is the default */
-	   -moz-perspective-origin: 50% 50%;
-	    -ms-perspective-origin: 50% 50%;
-	        perspective-origin: 50% 50%;
+	perspective: none;
+	perspective-origin: 50% 50%;
 }
 
 .reveal .slides .pdf-page {
@@ -103,15 +96,8 @@ ul, ol, div, p {
 
 	opacity: 1 !important;
 
-	-webkit-transform-style: flat !important;
-	   -moz-transform-style: flat !important;
-	    -ms-transform-style: flat !important;
-	        transform-style: flat !important;
-
-	-webkit-transform: none !important;
-	   -moz-transform: none !important;
-	    -ms-transform: none !important;
-	        transform: none !important;
+	transform-style: flat !important;
+	transform: none !important;
 }
 
 .reveal section.stack {