fix(cloudwatch): setting gauge widget annotations caused deployment failures (#27720)

A badly formed annotation was being added when annotations were set for gauge widgets (`yAxis: 'annotations'`). This caused errors on deployment. This change removes that extra annotation.

Closes #25496.

----

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

Author: scanlonp

packages/@aws-cdk-testing/framework-integ/test/aws-cloudwatch/test/integ.gauge-widget.js.snapshot/LambdaTestDefaultTestDeployAssert1AF2B360.assets.json

@@ -0,0 +1,55 @@
+{
+ "Resources": {
+  "Dashboard9E4231ED": {
+   "Type": "AWS::CloudWatch::Dashboard",
+   "Properties": {
+    "DashboardBody": {
+     "Fn::Join": [
+      "",
+      [
+       "{\"widgets\":[{\"type\":\"metric\",\"width\":6,\"height\":6,\"x\":0,\"y\":0,\"properties\":{\"view\":\"gauge\",\"title\":\"My gauge widget\",\"region\":\"",
+       {
+        "Ref": "AWS::Region"
+       },
+       "\",\"metrics\":[[\"AWS/VPN\",\"TunnelState\",\"TunnelIpAddress\",\"123.123.123.123\",{\"stat\":\"Minimum\"}]],\"annotations\":{\"horizontal\":[{\"color\":\"#b2df8d\",\"label\":\"Up\",\"value\":5,\"fill\":\"above\"}]},\"yAxis\":{\"left\":{\"min\":0,\"max\":10}},\"period\":60,\"stat\":\"Minimum\"}}]}"
+      ]
+     ]
+    }
+   }
+  }
+ },
+ "Parameters": {
+  "BootstrapVersion": {
+   "Type": "AWS::SSM::Parameter::Value<String>",
+   "Default": "/cdk-bootstrap/hnb659fds/version",
+   "Description": "Version of the CDK Bootstrap resources in this environment, automatically retrieved from SSM Parameter Store. [cdk:skip]"
+  }
+ },
+ "Rules": {
+  "CheckBootstrapVersion": {
+   "Assertions": [
+    {
+     "Assert": {
+      "Fn::Not": [
+       {
+        "Fn::Contains": [
+         [
+          "1",
+          "2",
+          "3",
+          "4",
+          "5"
+         ],
+         {
+          "Ref": "BootstrapVersion"
+         }
+        ]
+       }
+      ]
+     },
+     "AssertDescription": "CDK bootstrap stack version 6 required. Please run 'cdk bootstrap' with a recent version of the CDK CLI."
+    }
+   ]
+  }
+ }
+}