Bump actions/setup-python from 5 to 6

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 5 to 6.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](https://github.com/actions/setup-python/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/documentation.yml

diff --git a/.github/workflows/documentation.yml b/.github/workflows/documentation.yml
index 41cf7c3..3817776 100644
--- a/.github/workflows/documentation.yml
+++ b/.github/workflows/documentation.yml
@@ -18,7 +18,7 @@
     if: github.repository == 'web-platform-tests/wpt'
     steps:
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: '3.12'
       - name: Set up Node

.github/workflows/manifest.yml

diff --git a/.github/workflows/manifest.yml b/.github/workflows/manifest.yml
index 4ac2c8b..eec3c1f 100644
--- a/.github/workflows/manifest.yml
+++ b/.github/workflows/manifest.yml
@@ -12,7 +12,7 @@
     if: github.repository == 'web-platform-tests/wpt'
     steps:
     - name: Set up Python
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: '3.12'
     - name: Checkout

.github/workflows/regen_certs.yml

diff --git a/.github/workflows/regen_certs.yml b/.github/workflows/regen_certs.yml
index d60c6b0..d312a70 100644
--- a/.github/workflows/regen_certs.yml
+++ b/.github/workflows/regen_certs.yml
@@ -11,7 +11,7 @@
     if: github.repository == 'web-platform-tests/wpt'
     steps:
     - name: Set up Python
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: '3.12'
     - name: Checkout

.github/workflows/update_codeowners.yml

diff --git a/.github/workflows/update_codeowners.yml b/.github/workflows/update_codeowners.yml
index 9e3f23e..9dd99ef 100644
--- a/.github/workflows/update_codeowners.yml
+++ b/.github/workflows/update_codeowners.yml
@@ -9,7 +9,7 @@
     if: github.repository == 'web-platform-tests/wpt'
     steps:
     - name: Set up Python
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v6
       with:
         python-version: '3.12'
     - name: Checkout wpt