Internals: Update some JSON references. No functional change.

src/V3Scope.cpp

@@ -367,7 +367,7 @@ class ScopeCleanupVisitor final : public VNVisitor {
         iterateChildren(nodep);
     }
     void visit(AstModportFTaskRef* nodep) override {
-        // The modport persists only for xml dump
+        // The modport persists only for JSON dump
         // The crossrefs are dealt with in V3LinkDot
         nodep->ftaskp(nullptr);
         iterateChildren(nodep);