Remove redundant var declaration

Closes mathiasbynens#22.

Author: darrachequesne

utf8.js

@@ -157,7 +157,7 @@
 
 		// 2-byte sequence
 		if ((byte1 & 0xE0) == 0xC0) {
-			var byte2 = readContinuationByte();
+			byte2 = readContinuationByte();
 			codePoint = ((byte1 & 0x1F) << 6) | byte2;
 			if (codePoint >= 0x80) {
 				return codePoint;