fix: "Invalid Assembly Manifest" when used with CLI 2.1017.0 and 2.1018.0 (#34880)

`aws-cdk-lib` 2.203.0 gives an incorrect error message when used with AWS CLI 2.2017.0 and 2.2018.0. The error message should have been:

```
This CDK CLI is not compatible with the CDK library used by your application. Please upgrade the CLI to the latest version.
```

Instead, the error message is:

```
Invalid assembly manifest:
instance.artifacts.aws-cdk-lib/feature-flag-report.type is not one of enum values: none,aws:cloudformation:stack,cdk:tree,cdk:asset-manifest,cdk:cloud-assembly
...
```

This reverts the change that introduces that new artifact type: #34798

Author: rix0rrr

packages/aws-cdk-lib/core/lib/private/feature-flag-report.ts

@@ -15,7 +15,6 @@ import { Stack } from '../stack';
 import { ISynthesisSession } from '../stack-synthesizers/types';
 import { Stage, StageSynthesisOptions } from '../stage';
 import { IPolicyValidationPluginBeta1 } from '../validation';
-import { generateFeatureFlagReport } from './feature-flag-report';
 import { ConstructTree } from '../validation/private/construct-tree';
 import { PolicyValidationReportFormatter, NamedValidationPluginReport } from '../validation/private/report';
 
@@ -65,8 +64,6 @@ export function synthesize(root: IConstruct, options: SynthesisOptions = { }): c
   // stacks to add themselves to the synthesized cloud assembly.
   synthesizeTree(root, builder, options.validateOnSynthesis);
 
-  generateFeatureFlagReport(builder, root);
-
   const assembly = builder.buildAssembly();
 
   invokeValidationPlugins(root, builder.outdir, assembly);

packages/aws-cdk-lib/core/lib/private/synthesis.ts

@@ -252,7 +252,7 @@ describe('stage', () => {
     const rootAssembly = app.synth();
 
     // THEN
-    expect(rootAssembly.manifest.artifacts).toMatchObject({
+    expect(rootAssembly.manifest.artifacts).toEqual({
       'assembly-StageLevel1': {
         type: 'cdk:cloud-assembly',
         properties: {
@@ -263,7 +263,7 @@ describe('stage', () => {
     });
 
     const assemblyLevel1 = rootAssembly.getNestedAssembly('assembly-StageLevel1');
-    expect(assemblyLevel1.manifest.artifacts).toMatchObject({
+    expect(assemblyLevel1.manifest.artifacts).toEqual({
       'assembly-StageLevel1-StageLevel2': {
         type: 'cdk:cloud-assembly',
         properties: {
@@ -274,7 +274,7 @@ describe('stage', () => {
     });
 
     const assemblyLevel2 = assemblyLevel1.getNestedAssembly('assembly-StageLevel1-StageLevel2');
-    expect(assemblyLevel2.manifest.artifacts).toMatchObject({
+    expect(assemblyLevel2.manifest.artifacts).toEqual({
       'assembly-StageLevel1-StageLevel2-StageLevel3': {
         type: 'cdk:cloud-assembly',
         properties: {

packages/aws-cdk-lib/core/test/feature-flag-report.test.ts

@@ -24,7 +24,7 @@ describe('synthesis', () => {
     // THEN
     expect(app.synth()).toEqual(session); // same session if we synth() again
     expect(list(session.directory)).toEqual(['cdk.out', 'manifest.json', 'tree.json']);
-    expect(readJson(session.directory, 'manifest.json').artifacts).toMatchObject({
+    expect(readJson(session.directory, 'manifest.json').artifacts).toEqual({
       Tree: {
         type: 'cdk:tree',
         properties: { file: 'tree.json' },