[Automated] Update net-contour nightly

[knative-automation]

/assign @knative/serving-writers /cc @knative/serving-writers

Produced via:

for x in net-contour.yaml contour.yaml; do
  curl https://storage.googleapis.com/knative-nightly/net-contour/latest/$x > ${GITHUB_WORKSPACE}/./third_party/contour-latest/$x
done

Details:

bumping knative.dev/net-contour aac48c6...efcb75c:
  > efcb75c upgrade to latest dependencies (# 1108)

[knative-prow[bot]]

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.59%. Comparing base (a043ddf) to head (6b39973). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #15363 +/- ## ======================================= Coverage 84.59% 84.59% ======================================= Files 219 219 Lines 13584 13584 ======================================= Hits 11492 11492 - Misses 1725 1726 +1 + Partials 367 366 -1 ```

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