Correct bug in HttpSessionInvalidate

The `select` shouldn't be a `J.VariableDeclarations$NamedVariable`, but that variable's `J.Identifier`. This is important, because the former is not actually an instance of `Expression`, but this isn't detected due to Java's type erasure.

Author: knutwannheden

src/main/java/org/openrewrite/java/migrate/javax/HttpSessionInvalidate.java

@@ -76,7 +76,7 @@ public J.MethodInvocation visitMethodInvocation(J.MethodInvocation method, Execu
                             method = logoutTemplate.apply(
                                     getCursor(),
                                     method.getCoordinates().replace(),
-                                    httpServletRequestDeclaration.getVariables().get(0)
+                                    httpServletRequestDeclaration.getVariables().get(0).getName()
                             );
                         }
                         return super.visitMethodInvocation(method, ctx);