AK: Undo bogus Variant::downcast() rename

I accidentally renamed these to verify_cast() when doing the global
AK::downcast() rename.

AK/Variant.h

@@ -319,7 +319,7 @@ public:
     }
 
     template<typename... NewTs>
-    Variant<NewTs...> verify_cast() &&
+    Variant<NewTs...> downcast() &&
     {
         Variant<NewTs...> instance { Variant<NewTs...>::invalid_index, Detail::VariantConstructTag {} };
         visit([&](auto& value) {
@@ -331,7 +331,7 @@ public:
     }
 
     template<typename... NewTs>
-    Variant<NewTs...> verify_cast() &
+    Variant<NewTs...> downcast() &
     {
         Variant<NewTs...> instance { Variant<NewTs...>::invalid_index, Detail::VariantConstructTag {} };
         visit([&](const auto& value) {

Tests/AK/TestVariant.cpp

@@ -80,14 +80,14 @@ TEST_CASE(move_moves)
 TEST_CASE(verify_cast)
 {
     Variant<i8, i16, i32, i64> one_integer_to_rule_them_all { static_cast<i32>(42) };
-    auto fake_integer = one_integer_to_rule_them_all.verify_cast<i8, i32>();
+    auto fake_integer = one_integer_to_rule_them_all.downcast<i8, i32>();
     EXPECT(fake_integer.has<i32>());
     EXPECT(one_integer_to_rule_them_all.has<i32>());
     EXPECT_EQ(fake_integer.get<i32>(), 42);
     EXPECT_EQ(one_integer_to_rule_them_all.get<i32>(), 42);
 
     fake_integer = static_cast<i8>(60);
-    one_integer_to_rule_them_all = fake_integer.verify_cast<i8, i16>().verify_cast<i8, i32, float>().verify_cast<i8, i16, i32, i64>();
+    one_integer_to_rule_them_all = fake_integer.downcast<i8, i16>().downcast<i8, i32, float>().downcast<i8, i16, i32, i64>();
     EXPECT(fake_integer.has<i8>());
     EXPECT(one_integer_to_rule_them_all.has<i8>());
     EXPECT_EQ(fake_integer.get<i8>(), 60);

Userland/Libraries/LibJS/Parser.cpp

@@ -1691,7 +1691,7 @@ NonnullRefPtr<VariableDeclaration> Parser::parse_variable_declaration(bool for_l
 
         declarations.append(create_ast_node<VariableDeclarator>(
             { m_state.current_token.filename(), rule_start.position(), position() },
-            move(target).verify_cast<NonnullRefPtr<Identifier>, NonnullRefPtr<BindingPattern>>(),
+            move(target).downcast<NonnullRefPtr<Identifier>, NonnullRefPtr<BindingPattern>>(),
             move(init)));
 
         if (match(TokenType::Comma)) {

Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.cpp

@@ -397,7 +397,7 @@ Optional<InstantiationError> AbstractMachine::allocate_all_initial_phase(Module
 
             module_instance.exports().append(ExportInstance {
                 entry.name(),
-                move(address).verify_cast<FunctionAddress, TableAddress, MemoryAddress, GlobalAddress>(),
+                move(address).downcast<FunctionAddress, TableAddress, MemoryAddress, GlobalAddress>(),
             });
         }
     });