CI: no longer push subrepos (all repos are standalone)

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

.github/workflows/push_subrepos.yml

@@ -1,28 +0,0 @@
-name: Push to subrepositories
-on:
-  push:
-    branches:
-      - "main"
-    path:
-      - "libs/**"
-jobs:
-  push:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-        with:
-          # fetch full Git history, otherwise push-subrepos.sh would fail due to not being able to
-          # split the git subtree.
-          fetch-depth: 0
-      - name: Install git-filter-repo
-        run: python3 -m pip install --user git-filter-repo
-      - name: "Push recent commits to subrepositories"
-        env:
-          ACCESS_TOKEN: ${{ secrets.HEXOPS_MACH_PUSH_SUBREPOS }}
-        run: |
-          git config user.name 'Repository synchronization automation'
-          git config user.email 'stephen@hexops.com'
-          # See https://github.community/t/automating-push-to-public-repo/17742/12
-          git config -l | grep 'http\..*\.extraheader' | cut -d= -f1 | xargs -L1 git config --unset-all
-          ./.github/push-subrepos.sh