ubuntu to 24 and macos to 15

Author: yegor256

.github/workflows/mvn.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04, windows-2022, macos-12]
+        os: [ubuntu-24.04, windows-2022, macos-15]
         java: [11, 17]
     steps:
       - uses: actions/checkout@v4