docs: fix stale contribution and e2e debug instructions

[immanuwell]

A couple contributor docs are stale and trip people up a bit.

hack/README.md still points at master and uses git co, which fails on a normal git setup. DEVELOPMENT.md also points to test/rekt/scenarios and mentions TestMyRektScenario, but neither matches this repo.

How to repro

1. Run git co -b my-backport-branch upstream/release-X.Y
2. See git: 'co' is not a git command
3. Run git symbolic-ref refs/remotes/origin/HEAD and see refs/remotes/origin/main
4. Run test -d test/rekt/scenarios || echo missing
5. Run rg 'TestPingSourceWithSinkRef|TestMyRektScenario' test/rekt test -S

Fix is pretty small: use main, switch git co to git checkout, and align the e2e-debug.sh example with the real test and path. Tiny cleanup, but saves a weird faceplant

[knative-prow]

Hi @immanuwell. Thanks for your PR.

I'm waiting for a knative member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Tip

We noticed you've done this a few times! Consider joining the org to skip this step and gain /lgtm and other bot rights. We recommend asking approvers on your previous PRs to sponsor you.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.05%. Comparing base (69b976f) to head (4e55357).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9154   +/-   ##
=======================================
  Coverage   51.04%   51.05%           
=======================================
  Files         411      411           
  Lines       22132    22132           
=======================================
+ Hits        11298    11300    +2     
+ Misses       9960     9959    -1     
+ Partials      874      873    -1     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[creydr]

Thanks a lot @immanuwell

/ok-to-test
/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: creydr, immanuwell

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• OWNERS [creydr]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment