Update mac and windows CI to target for next release

It looks like our last release builds were done with python 3.11 and
PyQt 6.5.3. I'm expecting that since PyQt6.6 is out now our next release
will be on 6.6. So lets update the CI to match.

Questions:
* what about python12? I don't think there is a benefit to updating to
  that, so lets leave it.
* what about pyqt6.5? Do we care about testing that? Maybe for homebrew
  users? We aren't providing new builds with an old Qt right?

last release builds: https://github.com/qutebrowser/qutebrowser/actions/runs/6578864884

ref: https://github.com/qutebrowser/qutebrowser/issues/7989

.github/workflows/ci.yml

@@ -165,20 +165,20 @@ jobs:
           - testenv: py312-pyqt66
             os: ubuntu-22.04
             python: "3.12"
-          ### macOS Big Sur: PyQt 5.15 (Python 3.9 to match PyInstaller env)
-          - testenv: py39-pyqt515
+          ### macOS Big Sur
+          - testenv: py311-pyqt66
             os: macos-11
-            python: "3.9"
+            python: "3.11"
             args: "tests/unit"  # Only run unit tests on macOS
           ### macOS Monterey
-          - testenv: py39-pyqt515
+          - testenv: py311-pyqt66
             os: macos-12
-            python: "3.9"
+            python: "3.11"
             args: "tests/unit"  # Only run unit tests on macOS
-          ### Windows: PyQt 5.15 (Python 3.9 to match PyInstaller env)
-          - testenv: py39-pyqt515
+          ### Windows
+          - testenv: py311-pyqt66
             os: windows-2019
-            python: "3.9"
+            python: "3.11"
     runs-on: "${{ matrix.os }}"
     steps:
       - uses: actions/checkout@v4