fix: Button label case (#19706)

Json -> JSON
diff --git a/erpnext/regional/report/gstr_1/gstr_1.js b/erpnext/regional/report/gstr_1/gstr_1.js
index 9682768..ce55921 100644
--- a/erpnext/regional/report/gstr_1/gstr_1.js
+++ b/erpnext/regional/report/gstr_1/gstr_1.js
@@ -52,7 +52,7 @@
 	],
 	onload: function (report) {
 
-		report.page.add_inner_button(__("Download as Json"), function () {
+		report.page.add_inner_button(__("Download as JSON"), function () {
 			var filters = report.get_values();
 
 			const args = {