ci: update macos runners (#1511)

Following the GitHub runner roadmap:
actions/runner-images#9255

fixes #1508

.github/workflows/tests.yaml

@@ -47,7 +47,7 @@ jobs:
   run-tests:
     strategy:
       matrix:
-        os: [ubuntu-22.04, macos-11, macos-12, windows-2019, windows-2022]
+        os: [ubuntu-22.04, macos-12, macos-13, windows-2019, windows-2022]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout code

tests/integration/commands/test_init.py

@@ -18,7 +18,6 @@
 import contextlib
 import os
 import pathlib
-import platform
 import re
 import shutil
 import subprocess
@@ -222,10 +221,6 @@ def test_executable_set(new_path, init_command):
 
 @pytest.mark.slow()
 @pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
-@pytest.mark.xfail(
-    platform.system() == "Darwin" and platform.platform().startswith("macOS-11."),
-    reason="Currently failing on macos 11, see https://github.com/canonical/charmcraft/issues/1508",
-)
 @pytest.mark.skipif(bool(os.getenv("RUNNING_TOX")), reason="does not work inside tox")
 @pytest.mark.parametrize("profile", list(commands.init.PROFILES))
 def test_tox_success(new_path, init_command, profile):