refactor: Adopt J.Literal.isLiteralValue(expression, null) (#751)

Use this link to re-run the recipe: https://app.moderne.io/recipes/org.openrewrite.java.recipes.IsLiteralNullRecipe?organizationId=ODQ2MGExMTUtNDg0My00N2EwLTgzMGMtNGE1NGExMTBmZDkw

Co-authored-by: Moderne <team@moderne.io>

Author: timtebeek

src/main/java/org/openrewrite/java/testing/cleanup/AssertFalseNullToAssertNotNull.java

@@ -113,8 +113,8 @@ private boolean isEqualBinaryWithNull(J.MethodInvocation method) {
                 if (binary.getOperator() != J.Binary.Type.Equal) {
                     return false;
                 }
-                return binary.getLeft() instanceof J.Literal && ((J.Literal) binary.getLeft()).getValue() == null ||
-                       binary.getRight() instanceof J.Literal && ((J.Literal) binary.getRight()).getValue() == null;
+                return J.Literal.isLiteralValue(binary.getLeft(), null) ||
+                        J.Literal.isLiteralValue(binary.getRight(), null);
             }
         });
     }

src/main/java/org/openrewrite/java/testing/cleanup/AssertTrueNullToAssertNull.java

@@ -113,8 +113,8 @@ private boolean isEqualBinaryWithNull(J.MethodInvocation method) {
                 if (binary.getOperator() != J.Binary.Type.Equal) {
                     return false;
                 }
-                return binary.getLeft() instanceof J.Literal && ((J.Literal) binary.getLeft()).getValue() == null ||
-                       binary.getRight() instanceof J.Literal && ((J.Literal) binary.getRight()).getValue() == null;
+                return J.Literal.isLiteralValue(binary.getLeft(), null) ||
+                        J.Literal.isLiteralValue(binary.getRight(), null);
             }
         });
     }