Add scheme to some slack urls

Signed-off-by: Cintia Sanchez Garcia <cynthiasg@icloud.com>

landscape.yml

@@ -1189,7 +1189,7 @@ landscape:
             logo: kubelinter.svg
             crunchbase: https://www.crunchbase.com/organization/red-hat
             extra:
-              slack_url: kube-linter.slack.com
+              slack_url: https://kube-linter.slack.com
           - item:
             name: Kubescape
             description: >-
@@ -5532,7 +5532,7 @@ landscape:
                 - https://github.com/cncf/tag-app-delivery
               dev_stats_url: https://helm.devstats.cncf.io/
               artwork_url: https://github.com/cncf/artwork/blob/master/examples/incubating.md#helm-logos
-              slack_url: slack.k8s.io
+              slack_url: https://slack.k8s.io
               chat_channel: '#helm-dev'
               stack_overflow_url: https://stackoverflow.com/questions/tagged/helm
               clomonitor_name: helm
@@ -5567,7 +5567,7 @@ landscape:
             extra:
               accepted: '2022-12-14'
               dev_stats_url: https://ko.devstats.cncf.io/
-              slack_url: slack.k8s.io
+              slack_url: https://slack.k8s.io
               chat_channel: '#ko-build'
               clomonitor_name: ko
           - item:
@@ -5581,7 +5581,7 @@ landscape:
             extra:
               accepted: '2022-07-26'
               dev_stats_url: https://konveyor.devstats.cncf.io/
-              slack_url: slack.k8s.io
+              slack_url: https://slack.k8s.io
               chat_channel: '#konveyor'
               clomonitor_name: konveyor
               summary_personas: Enterprise Architects, Developers