Fix symbol for SZL currency

The symbol for the Swaziland (now Eswatini) Lilangeni is not L (for Lilangeni), 
but E (for Emalangeni, plural). Even if it is just one Lilangeni, it is written as
E1.00.

plugins/woocommerce/includes/wc-core-functions.php

@@ -801,7 +801,7 @@ function get_woocommerce_currency_symbols() {
 			'SSP' => '£',
 			'STN' => 'Db',
 			'SYP' => 'ل.س',
-			'SZL' => 'L',
+			'SZL' => 'E',
 			'THB' => '฿',
 			'TJS' => 'ЅМ',
 			'TMT' => 'm',