chore(scheduler-alpha): make LambdaInvoke prop optional (#31887)

### Issue # (if applicable)

None.

### Reason for this change

Improve ergonomics of the `LambdaInvoke` constructor signature. The second argument is not required so we should not force customers to pass in an empty object.

### Description of changes

Make the `LambdaInvoke` `prop` argument default to empty object.

### Description of how you validated changes

Unit test updated to omit the `prop` argument if no props are being passed.

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-scheduler-targets-alpha/lib/lambda-invoke.ts

@@ -11,7 +11,7 @@ export class LambdaInvoke extends ScheduleTargetBase implements IScheduleTarget
 
   constructor(
     func: lambda.IFunction,
-    props: ScheduleTargetBaseProps,
+    props: ScheduleTargetBaseProps = {},
   ) {
     super(props, func.functionArn);
     this.func = func;

packages/@aws-cdk/aws-scheduler-targets-alpha/test/lambda-invoke.test.ts

@@ -24,7 +24,7 @@ describe('schedule target', () => {
   });
 
   test('creates IAM role and IAM policy for lambda target in the same account', () => {
-    const lambdaTarget = new LambdaInvoke(func, {});
+    const lambdaTarget = new LambdaInvoke(func);
 
     new Schedule(stack, 'MyScheduleDummy', {
       schedule: expr,
@@ -89,7 +89,7 @@ describe('schedule target', () => {
     const lambdaVersion = new lambda.Version(stack, 'MyLambdaVersion', {
       lambda: func,
     });
-    const lambdaTarget = new LambdaInvoke(lambdaVersion, {});
+    const lambdaTarget = new LambdaInvoke(lambdaVersion);
 
     new Schedule(stack, 'MyScheduleDummy', {
       schedule: expr,
@@ -250,7 +250,7 @@ describe('schedule target', () => {
   test('creates IAM policy for imported lambda function in the same account', () => {
     const importedFunc = lambda.Function.fromFunctionArn(stack, 'ImportedFunction', 'arn:aws:lambda:us-east-1:123456789012:function/somefunc');
 
-    const lambdaTarget = new LambdaInvoke(importedFunc, {});
+    const lambdaTarget = new LambdaInvoke(importedFunc);
 
     new Schedule(stack, 'MyScheduleDummy', {
       schedule: expr,
@@ -295,7 +295,7 @@ describe('schedule target', () => {
       aliasName: 'SomeAliasName',
     });
 
-    const lambdaTarget = new LambdaInvoke(lambdaAlias, {});
+    const lambdaTarget = new LambdaInvoke(lambdaAlias);
 
     new Schedule(stack, 'MyScheduleDummy', {
       schedule: expr,
@@ -449,7 +449,7 @@ describe('schedule target', () => {
       },
     );
 
-    const lambdaTarget = new LambdaInvoke(importedFunc, {});
+    const lambdaTarget = new LambdaInvoke(importedFunc);
     new Schedule(stack, 'MyScheduleDummy', {
       schedule: expr,
       target: lambdaTarget,