Update CI workflow to use Ubuntu 24.04 and Python 3.14 stable (#386)

* Update CI workflow to use Ubuntu 24.04 and Python 3.14 stable

* Change CI runner from ubuntu-24.04 to ubuntu-22.04

* Update pytest command in CI workflow

Remove warning suppression for pytest on Python 3.6.

.github/workflows/ci.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ad45cca..c94fdf9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -33,7 +33,7 @@
         - "3.11"
         - "3.12"
         - "3.13"
-        - "3.14-dev"
+        - "3.14"
     steps:
     - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
     - name: Set up Python ${{ matrix.python-version }}
@@ -46,4 +46,4 @@
         python -m pip install pytest
     - name: Test with pytest
       run: |
-        python -W error -W 'ignore:Running attrs on Python 3.6' -m pytest
+        python -W error -m pytest