Update PR template not to mention changelog anymore

[dsimansk]

Description

Changes

• Update PR template not to mention changelog anymore

For a while now, we are fully on-boarded to automated Release Notes collection from PRs. This removes the leftover message that might be confusing.

Reference

Fixes #

Release Note

NONE

/cc @rhuss @vyasgun

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (a9ee31f) 79.62% compared to head (153dc7a) 79.62%. Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1848 +/- ## ======================================= Coverage 79.62% 79.62% ======================================= Files 179 179 Lines 13927 13927 ======================================= Hits 11090 11090 Misses 2070 2070 Partials 767 767 ```

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[dsimansk]

/retest

[rhuss]

/approve /lgtm

[knative-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dsimansk, rhuss

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/knative/client/blob/main/OWNERS)~~ [dsimansk,rhuss] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[rhuss]

/retest