Change the "Legacy" variables to amendment checks in visitNodes

- Having parallel variables is error prone in case of any future
  developments. It could also explode if another fix needs to be made
  later.

include/xrpl/tx/invariants/InvariantCheck.h

@@ -228,7 +228,6 @@ public:
 class NoXRPTrustLines
 {
     bool xrpTrustLine_ = false;
-    bool xrpTrustLineLegacy_ = false;
 
 public:
     void
@@ -248,7 +247,6 @@ public:
 class NoDeepFreezeTrustLinesWithoutFreeze
 {
     bool deepFreezeWithoutFreeze_ = false;
-    bool deepFreezeWithoutFreezeLegacy_ = false;
 
 public:
     void
@@ -284,7 +282,6 @@ public:
 class NoZeroEscrow
 {
     bool bad_ = false;
-    bool badLegacy_ = false;
 
 public:
     void