vagrant: use Python 3.11.3

3.11.2 had a compile failure on macos1012.

Vagrantfile

@@ -169,7 +169,7 @@ def install_pythons(boxname)
     . ~/.bash_profile
     echo "PYTHON_CONFIGURE_OPTS: ${PYTHON_CONFIGURE_OPTS}"
     pyenv install 3.12.6  # tests, binary build
-    pyenv install 3.11.2  # tests
+    pyenv install 3.11.3  # tests
     pyenv install 3.10.2  # tests
     pyenv install 3.9.4  # tests
     pyenv rehash
@@ -235,8 +235,8 @@ def run_tests(boxname, skip_env)
     . ../borg-env/bin/activate
     if which pyenv 2> /dev/null; then
       # for testing, use the earliest point releases of the supported python versions:
-      pyenv global 3.9.4 3.10.2 3.11.2 3.12.6
-      pyenv local 3.9.4 3.10.2 3.11.2 3.12.6
+      pyenv global 3.9.4 3.10.2 3.11.3 3.12.6
+      pyenv local 3.9.4 3.10.2 3.11.3 3.12.6
     fi
     # otherwise: just use the system python
     # some OSes can only run specific test envs, e.g. because they miss FUSE support: