chore: change macos test image

Author: yeshan333

.github/workflows/e2e_test.yaml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         # ref: https://github.com/actions/runner-images
-        os: [ubuntu-20.04, macos-13]
+        os: [ubuntu-20.04, macos-12]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4

README.md

@@ -51,7 +51,7 @@ vfox use -g elixir@1.16.2
 
 You can reference the E2E test in Ubuntu 20.04: [https://github.com/version-fox/vfox-elixir/actions/workflows/e2e_test.yaml](https://github.com/version-fox/vfox-elixir/actions/workflows/e2e_test.yaml)
 
-### install in Darwin (MacOS 13)
+### install in Darwin (MacOS 12)
 
 ```shell
 # install utilities
@@ -68,4 +68,4 @@ vfox install elixir@1.16.2
 vfox use -g elixir@1.16.2
 ```
 
-You can reference the E2E test in MacOS 13: [https://github.com/version-fox/vfox-elixir/actions/workflows/e2e_test.yaml](https://github.com/version-fox/vfox-elixir/actions/workflows/e2e_test.yaml)
+You can reference the E2E test in MacOS 12: [https://github.com/version-fox/vfox-elixir/actions/workflows/e2e_test.yaml](https://github.com/version-fox/vfox-elixir/actions/workflows/e2e_test.yaml)