Fix some minor issues in landscape.yml file (cncf#3442)

- Fix format of a couple of dates
- Remove references to a couple of repositories that no longer exist

Signed-off-by: Cintia Sanchez Garcia <cynthiasg@icloud.com>
Signed-off-by: Lars Larsson <lars.larsson@elastisys.com>

landscape.yml

@@ -3155,7 +3155,7 @@ landscape:
             logo: clusternet.svg
             crunchbase: https://www.crunchbase.com/organization/cloud-native-computing-foundation
             extra:
-              accepted: 2023-03-07T00:00:00.000Z
+              accepted: '2023-03-07'
               dev_stats_url: https://clusternet.devstats.cncf.io/
               slack_url: https://cloud-native.slack.com/messages/clusternet
               clomonitor_name: clusternet
@@ -4142,7 +4142,6 @@ landscape:
           - item:
             name: Gloo Mesh
             homepage_url: https://docs.solo.io/gloo-mesh-enterprise/latest
-            repo_url: https://github.com/solo-io/gloo-mesh
             logo: gloomesh.svg
             crunchbase: https://www.crunchbase.com/organization/solo-io
           - item:
@@ -6446,7 +6445,7 @@ landscape:
             twitter: https://twitter.com/pipecd_dev
             crunchbase: https://www.crunchbase.com/organization/cloud-native-computing-foundation
             extra:
-              accepted: 2023-05-17T00:00:00.000Z
+              accepted: '2023-05-17'
               dev_stats_url: https://pipecd.devstats.cncf.io/
               slack_url: https://cloud-native.slack.com/messages/pipecd
               blog_url: https://pipecd.dev/blog/
@@ -7267,7 +7266,6 @@ landscape:
               AKS Engine provides convenient tooling to quickly bootstrap Kubernetes clusters on Azure Stack. By leveraging ARM (Azure Resource Manager), AKS
               Engine helps create, destroy and maintain clusters provisioned with basic IaaS resources in Azure Stack.
             homepage_url: https://docs.microsoft.com/en-us/azure-stack/user/azure-stack-kubernetes-aks-engine-overview?view=azs-2108
-            repo_url: https://github.com/msazurestackworkloads/aks-engine
             logo: microsoft-azure.svg
             twitter: https://twitter.com/Azure
             crunchbase: https://www.crunchbase.com/organization/microsoft