Match CONTRIBUTING language to existing copyright notices

Also fixes some copy-pasted comments in a few devel/ scripts

Signed-off-by: Ashley Davis <ashley.davis@jetstack.io>

CONTRIBUTING.md

@@ -4,16 +4,16 @@ You can find our full contributing guide on [our website](https://cert-manager.i
 
 ## DCO Sign off
 
-All authors to the project retain copyright to their work. However, to ensure
-that they are only submitting work that they have rights to, we are requiring
+All contributors to the project retain copyright to their work. However, to ensure
+that they are only submitting work that they have rights to, we require
 everyone to acknowledge this by signing their work.
 
-Any copyright notices in this repo should specify the authors as "the Jetstack
-cert-manager contributors".
+Any copyright notices in this repo should specify the authors as
+"The cert-manager Authors".
 
 To sign your work, just add a line like this at the end of your commit message:
 
-```
+```text
 Signed-off-by: Joe Bloggs <joe@example.com>
 ```
 
@@ -23,7 +23,7 @@ You can also mass sign-off a whole PR with `git rebase --signoff master`, replac
 
 By doing this you state that you can certify the following (from https://developercertificate.org/):
 
-```
+```text
 Developer Certificate of Origin
 Version 1.1
 
@@ -61,4 +61,4 @@ By making a contribution to this project, I certify that:
     personal information I submit with it, including my sign-off) is
     maintained indefinitely and may be redistributed consistent with
     this project or the open source license(s) involved.
-```
+```

devel/addon/certmanager/install.sh

@@ -44,13 +44,13 @@ load_image "quay.io/jetstack/cert-manager-cainjector:${APP_VERSION}" &
 load_image "quay.io/jetstack/cert-manager-webhook:${APP_VERSION}" &
 wait
 
-# Ensure the pebble namespace exists
+# Ensure the namespace exists, and if not create it
 kubectl get namespace "${NAMESPACE}" || kubectl create namespace "${NAMESPACE}"
 
 # Build the Helm chart package .tgz
 bazel build //deploy/charts/cert-manager
 
-# Upgrade or install Pebble
+# Upgrade or install cert-manager
 helm upgrade \
     --install \
     --wait \

devel/addon/pebble/install.sh

@@ -38,7 +38,7 @@ check_tool kubectl
 check_tool helm
 require_image "pebble:bazel" "//devel/addon/pebble:bundle"
 
-# Ensure the pebble namespace exists
+# Ensure the namespace exists, and if not create it
 kubectl get namespace "${NAMESPACE}" || kubectl create namespace "${NAMESPACE}"
 
 # Upgrade or install Pebble

devel/addon/samplewebhook/install.sh

@@ -37,10 +37,10 @@ check_tool kubectl
 check_tool helm
 require_image "sample-webhook:bazel" "//devel/addon/samplewebhook:bundle"
 
-# Ensure the pebble namespace exists
+# Ensure the namespace exists, and if not create it
 kubectl get namespace "${NAMESPACE}" || kubectl create namespace "${NAMESPACE}"
 
-# Upgrade or install Pebble
+# Upgrade or install the sample-webhook
 helm upgrade \
     --install \
     --wait \