chore: Fix markdown in CONTRIBUTING.md

[kahowell]

Description

Namely,

• fix sync process link
• put empty lines around lists
• remove trailing whitespace
• remove trailing colon in heading
• add newline to end-of-file

Found with markdownlint-cli2 locally

How Has This Been Tested?

Screenshot or short clip

Merge criteria

• You have read the contributors guide.
• Commit messages are meaningful - have a clear and concise summary and detailed explanation of what was changed and why.
• Pull Request contains a description of the solution, a link to the JIRA issue, and to any dependent or related Pull Request.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work

[kahowell]

/label documentation

[openshift-ci]

@kahowell: The label(s) /label documentation cannot be applied. These labels are supported: acknowledge-critical-fixes-only, platform/aws, platform/azure, platform/baremetal, platform/google, platform/libvirt, platform/openstack, ga, tide/merge-method-merge, tide/merge-method-rebase, tide/merge-method-squash, px-approved, docs-approved, qe-approved, ux-approved, no-qe, downstream-change-needed, rebase/manual, cluster-config-api-changed, approved, backport-risk-assessed, bugzilla/valid-bug, cherry-pick-approved, jira/valid-bug, stability-fix-approved, staff-eng-approved. Is this label configured under labels -> additional_labels or labels -> restricted_labels in plugin.yaml?

In response to this:

/label documentation

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 24.27%. Comparing base (89ce6d7) to head (8ca2ac6).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1777      +/-   ##
==========================================
+ Coverage   24.10%   24.27%   +0.17%     
==========================================
  Files         172      172              
  Lines       11763    11790      +27     
==========================================
+ Hits         2835     2862      +27     
  Misses       8650     8650              
  Partials      278      278              

☔ View full report in Codecov by Sentry.
📢 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.

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zdtsw

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

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [zdtsw]

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