Release tool output should be alphabetically sorted irrespective of their upper/lower case

[nawazkh]

What steps did you take and what happened?

The output of the release tool , although sorted, segregates uppercase prefixed PRs and lowercase prefixed PRs.
Example:

.
.
Devtools: tilt: set CR logger in tilt-prepare, fix allowed contexts
IPAM: ipam: fix gateway being required for IPAddress 
KCP: Allow machine rollout if cert reconcile fails
.
.
e2e: test/e2e check for machines being ready after provisioning on Runtime SDK test 
e2e: test/e2e: use topology cluster-template for clusterctl upgrade mgmt cluster
.
.

What did you expect to happen?

We would want to club all the PRs together and sort them irrespective of the case of the prefix of the PR.
The output should look like

.
.
Devtools: tilt: set CR logger in tilt-prepare, fix allowed contexts
e2e: test/e2e check for machines being ready after provisioning on Runtime SDK test 
e2e: test/e2e: use topology cluster-template for clusterctl upgrade mgmt cluster
IPAM: ipam: fix gateway being required for IPAddress 
KCP: Allow machine rollout if cert reconcile fails
.
.

Cluster API version

unrelated to CAPI version

Kubernetes version

unrelated to K8s version

Anything else you would like to add?

Should be part of #9008

Label(s) to be applied

/kind bug
One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels.

[killianmuldoon]

/triage accepted

[Dhairya-Arora01]

/assign