Revert "fix for line-height that makes emojis be perfectly aligned with text"

This reverts commit 19907ff8e0.

lib/hterm.js

@@ -147,7 +147,7 @@ hterm.Terminal.prototype.setFontSize = function (px) {
   unicodeNodeStyle.innerHTML = `
     .unicode-node {
       display: inline-block;
-      vertical-align: middle;
+      vertical-align: top;
       width: ${this.scrollPort_.characterSize.width}px;
     }
   `;