update drone syntax for 1.x

.drone.yml

-pipeline:
-  lint-charts:
-    image: guangbo/chart-testing:v2.0.2-rancher1
-    commands:
-      - git remote add rancher-charts https://github.com/rancher/charts
-      - git fetch rancher-charts master
-      - ct lint --config test/ct.yaml
+---
+kind: pipeline
+name: default
+
+platform:
+  os: linux
+  arch: amd64
+
+steps:
+- name: lint-charts
+  pull: default
+  image: guangbo/chart-testing:v2.0.2-rancher1
+  commands:
+  - git remote add rancher-charts https://github.com/rancher/charts
+  - git fetch rancher-charts master
+  - ct lint --config test/ct.yaml