feat!: use stable synthetics module (#435)

BREAKING CHANGE: requires aws-cdk-lib@^2.99.0

The Synthetics module was promoted to stable in https://github.com/aws/aws-cdk/releases/tag/v2.99.0.

---

_By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license_

.projenrc.ts

@@ -1,6 +1,6 @@
 import { awscdk, javascript, github, DependencyType } from "projen";
 
-const CDK_VERSION = "2.65.0";
+const CDK_VERSION = "2.99.0";
 
 const project = new awscdk.AwsCdkConstructLibrary({
   name: "cdk-monitoring-constructs",
@@ -11,7 +11,7 @@ const project = new awscdk.AwsCdkConstructLibrary({
   keywords: ["cloudwatch", "monitoring"],
 
   defaultReleaseBranch: "main",
-  majorVersion: 5,
+  majorVersion: 6,
   stability: "experimental",
 
   cdkVersion: CDK_VERSION,
@@ -69,20 +69,18 @@ _By submitting this pull request, I confirm that my contribution is made under t
 });
 
 // Experimental modules
-[
-  "@aws-cdk/aws-apigatewayv2-alpha",
-  "@aws-cdk/aws-redshift-alpha",
-  "@aws-cdk/aws-synthetics-alpha",
-].forEach((dep) => {
-  project.deps.addDependency(
-    `${dep}@^${CDK_VERSION}-alpha.0`,
-    DependencyType.PEER
-  );
-  project.deps.addDependency(
-    `${dep}@${CDK_VERSION}-alpha.0`,
-    DependencyType.DEVENV
-  );
-});
+["@aws-cdk/aws-apigatewayv2-alpha", "@aws-cdk/aws-redshift-alpha"].forEach(
+  (dep) => {
+    project.deps.addDependency(
+      `${dep}@^${CDK_VERSION}-alpha.0`,
+      DependencyType.PEER
+    );
+    project.deps.addDependency(
+      `${dep}@${CDK_VERSION}-alpha.0`,
+      DependencyType.DEVENV
+    );
+  }
+);
 // https://github.com/DefinitelyTyped/DefinitelyTyped/discussions/60310
 project.deps.addDependency("@types/[email protected]", DependencyType.DEVENV);