Format copyright headers to match boilerplate

[antoineco]

Proposed Changes

• Run sed on the entire codebase to format copyright headers that diverge from the project's boilerplate

The "Boilerplate Check" GitHub Action reports those drifts on new PRs, but not for files that already existed in the repo before the check was introduced.

[codecov]

Codecov Report

Merging #1962 (2228c3a) into master (c35cc6b) will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1962      +/-   ##
==========================================
+ Coverage   68.92%   68.96%   +0.04%     
==========================================
  Files         209      209              
  Lines        8778     8778              
==========================================
+ Hits         6050     6054       +4     
+ Misses       2453     2451       -2     
+ Partials      275      273       -2     

Impacted Files	Coverage Δ
source/source_labels.go	100.00% <ø> (ø)
source/source_stats_reporter.go	85.71% <ø> (ø)
test/upgrade/functions.go	100.00% <ø> (ø)
test/upgrade/steps.go	96.84% <ø> (ø)
test/upgrade/suite_execution.go	92.68% <ø> (ø)
test/upgrade/vars.go	0.00% <ø> (ø)
test/gcs/mock/mock.go	92.47% <0.00%> (+2.15%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c35cc6b...2228c3a. Read the comment docs.

[markusthoemmes]

/lgtm
/approve

Thanks!

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: antoineco, markusthoemmes

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:

• apis/OWNERS [markusthoemmes]
• source/OWNERS [markusthoemmes]
• test/OWNERS [markusthoemmes]

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