fix: db.get_value -> db.get_single_value (#17531)

db.get_value for singles returns string type always, this is confusing
behaviour, db.get_single_value should be used instead.

semgrep rule: https://github.com/frappe/semgrep-rules/pull/16

payments/templates/pages/razorpay_checkout.py

@@ -51,7 +51,7 @@ def get_context(context):
 
 
 def get_api_key():
-	api_key = frappe.db.get_value("Razorpay Settings", None, "api_key")
+	api_key = frappe.db.get_single_value("Razorpay Settings", "api_key")
 	if cint(frappe.form_dict.get("use_sandbox")):
 		api_key = frappe.conf.sandbox_api_key