Revert "chore: use latest swift version"

This reverts commit e93f372.

Author: pine

.github/workflows/test.yml

@@ -9,16 +9,11 @@ jobs:
   build:
     strategy:
       matrix:
-        include:
-          - os: macos-15
-            swift-version: 5
-          - os: macos-15
-            swift-version: 6
+        os:
+          - macos-14
+          - macos-15
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: swift-actions/setup-swift@682457186b71c25a884c45c06f859febbe259240 # v2.3.0
-        with:
-          swift-version: ${{ matrix.swift-version }}
       - name: Checkout
         uses: actions/checkout@v4
       - name: Get swift version