Add support for the 'TicketBatch' amendment:

Support for 'out-of-sequence' transaction execution was introduced
in commit 7724cca384.

The changes in that commit were gated under a feature but there was
no corresponding amendment introduced that would allow the network
to vote on this amendment.

This commit introduces 'TicketBatch' amendment as the amendment
that is associated with the tickets feature. If the amendment is
enabled, it will activate support for tickets.

This commit also removes several workarounds that are no longer
needed in unit tests.

src/test/app/DepositAuth_test.cpp

@@ -434,7 +434,7 @@ struct DepositPreauth_test : public beast::unit_test::suite
         {
             // Verify that an account can be preauthorized and unauthorized
             // using tickets.
-            Env env(*this, supported_amendments() | featureTicketBatch);
+            Env env(*this);
             env.fund(XRP(10000), alice, becky);
             env.close();
 
@@ -729,7 +729,7 @@ struct DepositPreauth_test : public beast::unit_test::suite
     {
         testEnable();
         testInvalid();
-        auto const supported{jtx::supported_amendments() | featureTicketBatch};
+        auto const supported{jtx::supported_amendments()};
         testPayment(supported - featureDepositPreauth);
         testPayment(supported);
     }