Remove deprecated pipeline resources from Triggers tutorial

[dibyom]

          > Error from server (BadRequest): error when creating "/home/prow/go/src/github.com/tektoncd/triggers/docs/getting-started/pipeline.yaml": admission webhook "validation.webhook.pipeline.tekton.dev" denied the request: validation failed: invalid value: cloudEvent: spec.resources.outputs[0].event-to-sink.type

Originally posted by @dibyom in #1511 (comment)

Plan

Looks like we actually have to rewrite our getting-started pipeline significantly

• Replace git resource with git-clone task (can be based off of https://github.com/tektoncd/pipeline/blob/main/examples/v1beta1/pipelineruns/pipelinerun.yaml)
• Replace build-docker-image task with https://hub.tekton.dev/tekton/task/kaniko - use remote resolution instead of adding yaml (Improving remote resolution docs pipeline#6045)
• Rewrite deploy-locally task to use a workspace for input
• Replace cloud event resource usage #1522
• Update triggers.yaml template to use the new pipelinerun