chore: remove unneeded gcc13 ci tests

.github/workflows/ubuntu22-gcc13.yml

@@ -1,23 +0,0 @@
-name: Ubuntu 24.04 CI (GCC 13)
-
-on: [push, pull_request]
-
-jobs:
-  ubuntu-build:
-    if: >-
-      ! contains(toJSON(github.event.commits.*.message), '[skip ci]') &&
-      ! contains(toJSON(github.event.commits.*.message), '[skip github]')
-    runs-on: ubuntu-24.04
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/cache@v4
-        with:
-          path: dependencies/.cache
-          key: ${{ hashFiles('dependencies/CMakeLists.txt') }}
-      - name: Use cmake
-        run: |
-          mkdir build &&
-          cd build &&
-          CXX=g++-13 cmake -DSIMDJSON_DEVELOPER_MODE=ON ..  &&
-          cmake --build .   &&
-          ctest --output-on-failure -LE explicitonly -j