Don't bother pinning OS images for Github Actions

Fix #1612

The hassle of updating these pins (both for us and our users, most copy our documentation) seems to outweigh the benefit of the pin. The truth is that they're not really pins anyway, Github update them all the time, and they don't work for historical repeatability because old images are retired all the time.

.github/workflows/test.yml

@@ -38,10 +38,10 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04, windows-latest, macos-11]
+        os: [ubuntu-latest, windows-latest, macos-latest]
         python_version: ['3.12']
         include:
-        - os: ubuntu-22.04
+        - os: ubuntu-latest
           python_version: '3.8'
     timeout-minutes: 180
     steps:

.github/workflows/update-dependencies.yml

@@ -18,7 +18,7 @@ jobs:
   update-dependencies:
     name: Update dependencies
     if: github.repository_owner == 'pypa' || github.event_name != 'schedule'
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
 

README.md

@@ -88,7 +88,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04, windows-2019, macOS-11]
+        os: [ubuntu-latest, windows-latest, macOS-latest]
 
     steps:
       - uses: actions/checkout@v4

docs/setup.md

@@ -178,7 +178,7 @@ To build Linux, Mac, and Windows wheels using GitHub Actions, create a `.github/
         runs-on: ${{ matrix.os }}
         strategy:
           matrix:
-            os: [ubuntu-20.04, windows-2019, macos-11]
+            os: [ubuntu-latest, windows-latest, macos-latest]
 
         steps:
           - uses: actions/checkout@v4
@@ -211,7 +211,7 @@ To build Linux, Mac, and Windows wheels using GitHub Actions, create a `.github/
         runs-on: ${{ matrix.os }}
         strategy:
           matrix:
-            os: [ubuntu-20.04, windows-2019, macos-11]
+            os: [ubuntu-latest, windows-latest, macos-latest]
 
         steps:
           - uses: actions/checkout@v4

examples/github-apple-silicon.yml

@@ -5,7 +5,7 @@ on: [push, pull_request]
 jobs:
   build_wheels_macos:
     name: Build wheels on macos-11
-    runs-on: macos-11
+    runs-on: macos-latest
     steps:
       - uses: actions/checkout@v4
 

examples/github-deploy.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-22.04, windows-2022, macos-11]
+        os: [ubuntu-latest, windows-latest, macos-latest]
 
     steps:
       - uses: actions/checkout@v4

examples/github-minimal.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04, windows-2019, macos-11]
+        os: [ubuntu-latest, windows-latest, macos-latest]
 
     steps:
       - uses: actions/checkout@v4

examples/github-with-qemu.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04, windows-2019, macos-11]
+        os: [ubuntu-latest, windows-latest, macos-latest]
 
     steps:
       - uses: actions/checkout@v4