Fix trigger_comment newline

Fix yaml in prow.yaml PR or it would cause issues to the controller not
being able to parse it.

The pac controller would get:

🚨 11:31:31 pac-controller prun:  tekton validation error: yaml: line
16: could not find expected ':'

it's all deep down inside the decoder method:

decoder := k8scheme.Codecs.UniversalDeserializer()

so nothing we can really do on our side, and we have to tell our users
to have to use the |- thing instead.

Signed-off-by: Chmouel Boudjnah <[email protected]>

.tekton/prow.yaml

@@ -9,7 +9,7 @@ metadata:
 spec:
   params:
     - name: trigger_comment
-      value: |
+      value: |-
         {{ trigger_comment }}
     - name: repo_owner
       value: "{{ repo_owner }}"

docs/content/docs/guide/authoringprs.md

@@ -87,7 +87,7 @@ You will encounter a YAML validation error because objects or multiline strings
 spec:
   params:
     - name: body
-      value: |
+      value: |-
         {{ body }}
     # Alternatively, use '>' to specify that the value will be in block format
     - name: pull_request