Twenty Fourteen: Correct video play button position.

A change to the MediaElement.js caused Twenty Fourteen's custom video play button to display in the top corner, rather than centered. This update returns it to its correct position. 

Props mmaumio, celloexpressions.
Merges [44380] to the 5.0 branch.
Fixes #44664.

git-svn-id: https://develop.svn.wordpress.org/branches/5.0@44421 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-content/themes/twentyfourteen/css/editor-style.css

@@ -628,7 +628,6 @@ img {
 	box-shadow: 1px 1px 1px rgba(0,0,0,.8);
 	color: #000;
 	height: 36px;
-	margin-left: -24px;
 	width: 48px;
 }
 
@@ -637,7 +636,7 @@ img {
 	content: '\f452';
 	display: inline-block;
 	font: normal 32px/1.125 Genericons;
-	position: absolute;
+	position: relative;
 	top: 1px;
 	left: 10px;
 }

src/wp-content/themes/twentyfourteen/style.css

@@ -1405,7 +1405,6 @@ a.post-thumbnail:hover {
 	box-shadow: 1px 1px 1px rgba(0,0,0,.8);
 	color: #000;
 	height: 36px;
-	margin: -28px 0 0 -24px; /* Keep centered on video (container includes visible controls bar) */
 	width: 48px;
 }
 
@@ -1415,7 +1414,7 @@ a.post-thumbnail:hover {
 	content: '\f452';
 	display: inline-block;
 	font: normal 32px/1.125 Genericons;
-	position: absolute;
+	position: relative;
 	top: 1px;
 	left: 10px;
 }