Remove drone integration

Note: this also removes the FOSSA step! Be sure we create an issue
to re-add this at a later date, if we decide to do that.

.drone.yml

@@ -1,59 +0,0 @@
----
-kind: pipeline
-name: fossa
-
-steps:
-  - name: fossa
-    image: rancher/drone-fossa:latest
-    settings:
-      api_key:
-        from_secret: FOSSA_API_KEY
-    when:
-      instance:
-        include:
-          - drone-publish.rancher.io
-        exclude:
-          - drone-pr.rancher.io
----
-kind: pipeline
-name: build
-
-steps:
-  - name: build
-    image: registry.suse.com/bci/golang:1.22
-    commands:
-      - make build-bin
-    when:
-      event:
-        - push
-        - pull_request
----
-kind: pipeline
-name: validate
-
-steps:
-  - name: validate
-    image: registry.suse.com/bci/bci-base:15.6
-    commands:
-      - zypper in -y "golang(API)=1.22" git tar gzip make
-      - curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s v1.57.1
-      - mv ./bin/golangci-lint /usr/local/bin/golangci-lint
-      - GOBIN=/usr/local/bin go install github.com/golang/mock/mockgen@v1.6.0
-      - make validate
-    when:
-      event:
-        - push
-        - pull_request
----
-kind: pipeline
-name: test
-
-steps:
-  - name: test
-    image: registry.suse.com/bci/golang:1.22
-    commands:
-      - make test
-    when:
-      event:
-        - push
-        - pull_request