use double quotes

Co-authored-by: Dviih <[email protected]>
Signed-off-by: Zefir <[email protected]>

Author: zefir-git

src/main/resources/config.yml

@@ -539,7 +539,7 @@ messages:
         # Used in the <status> placeholder
         # Same placeholders as details (except <status>)
         status:
-            paid: '<green>Paid</green> <gray>(transaction #<transaction-id>)</gray>'
+            paid: "<green>Paid</green> <gray>(transaction #<transaction-id>)</gray>"
             unpaid: <gray>Unpaid</gray>
 
         # Used in the <pay-button> placeholder. This placeholder is an empty string if the invoice is unpaid.