Update not bull button title (#407)

* Fix button behavior: Reverse logic for nullable/not nullable toggle

* fix: updated translation key to 'nullable' and refactored button title

src/i18n/locales/en.js

@@ -113,6 +113,7 @@ const en = {
     type: "Type",
     null: "Null",
     not_null: "Not null",
+    nullable: "Nullable",
     primary: "Primary",
     unique: "Unique",
     autoincrement: "Autoincrement",

src/i18n/locales/tm.js

@@ -113,6 +113,7 @@ const tm = {
     type: "வகை",
     null: "பூஜ்ஜியம்",
     not_null: "பூஜ்ஜியம் அல்ல",
+    nullable: "காலியாக அனுமதி",
     primary: "முதன்மை",
     unique: "தனித்துவம்",
     autoincrement: "தானாக அதிகரிப்பு",