Delete not needed gitpod.yml file in the webapp (#25667)

* Delete webapp/channels/.gitpod.yml

* Delete api/.gitpod.yml

api/.gitpod.yml

@@ -1,15 +0,0 @@
-ports:
-  - port: 8080
-    onOpen: open-browser
-
-tasks:
-  - name: Docs
-    init: make build
-    command: make run
-  - name: Notice
-    command: |
-      clear
-      echo "Once the docs server is running, go to the following URL to view the docs:
-
-      $(gp url 8080)"
-    openMode: split-right

webapp/channels/.gitpod.yml

@@ -1 +0,0 @@
-mainConfiguration: https://github.com/mattermost/mattermost-gitpod-config