AK+Everywhere: Delete Variant's default constructor

This was exposed to the user by mistake, and even accumulated a bunch of
users that didn't blow up out of sheer luck.

Userland/Libraries/LibSQL/Value.h

@@ -102,7 +102,7 @@ private:
     SQLType m_type { SQLType::Text };
     bool m_is_null { true };
 
-    Variant<String, int, double> m_impl {};
+    Variant<String, int, double> m_impl;
 };
 
 }