fix: Correct South Africa VAT Rate (#25894)

On 1 April 2018 South Africa increased the VAT rate from 14% to 15%, this proposed change seeks to update the default parameters for a fresh ERPNext installation.
diff --git a/erpnext/setup/setup_wizard/data/country_wise_tax.json b/erpnext/setup/setup_wizard/data/country_wise_tax.json
index ec9a6d6..daaa626 100644
--- a/erpnext/setup/setup_wizard/data/country_wise_tax.json
+++ b/erpnext/setup/setup_wizard/data/country_wise_tax.json
@@ -1867,7 +1867,7 @@
 	"South Africa": {
 		"South Africa Tax": {
 			"account_name": "VAT",
-			"tax_rate": 14.00
+			"tax_rate": 15.00
 		}
 	},