Use ko:// in e2e tests to exercices current code 🙃

Right now, some examples are exercicing old version of the code, and
definitely never the changes that would be on the images in a PR.
Using `ko://` instead helps with that (e2e tests are using `ko` to
apply the samples).

Signed-off-by: Vincent Demeester <vdemeest@redhat.com>

examples/v1beta1/pipelineruns/pipelinerun-with-final-tasks.yaml

@@ -57,7 +57,7 @@ spec:
       description: The precise commit SHA that was fetched by this Task
   steps:
     - name: clone
-      image: gcr.io/tekton-releases/github.com/tektoncd/pipeline/cmd/git-init:v0.12.1
+      image: ko://github.com/tektoncd/pipeline/cmd/git-init
       script: |
         CHECKOUT_DIR="$(workspaces.output.path)/$(params.subdirectory)"
 

examples/v1beta1/pipelineruns/pipelinerun.yaml

@@ -80,7 +80,7 @@ spec:
     description: The precise commit SHA that was fetched by this Task
   steps:
   - name: clone
-    image: gcr.io/tekton-releases/github.com/tektoncd/pipeline/cmd/git-init:v0.11.0
+    image: ko://github.com/tektoncd/pipeline/cmd/git-init
     script: |
       CHECKOUT_DIR="$(workspaces.output.path)/$(params.subdirectory)"
       cleandir() {
@@ -167,7 +167,7 @@ spec:
       runAsUser: 0
   - name: write-digest
     workingDir: $(workspaces.source.path)
-    image: gcr.io/tekton-releases/github.com/tektoncd/pipeline/cmd/imagedigestexporter:v0.11.1
+    image: ko://github.com/tektoncd/pipeline/cmd/imagedigestexporter
     # output of imagedigestexport [{"name":"image","digest":"sha256:eed29..660"}]
     command: ["/ko-app/imagedigestexporter"]
     args: