remove test_build.yml: unmaintained and redundant

it seems this action has not been run for nealry a year. it has only
been run twice at all. it is not maintained, as it uses older Node.js
in particular. also, it seems to be redundant to build.yml, which
already builds firmware for every commit.

.github/workflows/test_build.yml

@@ -1,103 +0,0 @@
-name: OpenDTU-onBattery Test Build
-
-on: workflow_dispatch
-
-jobs:
-  get_default_envs:
-    name: Gather Environments
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-
-      - name: Cache pip
-        uses: actions/cache@v3
-        with:
-          path: ~/.cache/pip
-          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
-          restore-keys: |
-            ${{ runner.os }}-pip-
-
-      - uses: actions/setup-python@v4
-        with:
-          python-version: "3.9"
-
-      - name: Install PlatformIO
-        run: |
-          python -m pip install --upgrade pip
-          pip install --upgrade platformio
-
-      - name: Get default environments
-        id: envs
-        run: |
-          echo "environments=$(pio project config --json-output | jq -cr '.[1][1][0][1]|split(",")')" >> $GITHUB_OUTPUT
-
-    outputs:
-      environments: ${{ steps.envs.outputs.environments }}
-
-  build:
-    name: Build Enviornments
-    runs-on: ubuntu-latest
-    needs: get_default_envs
-    strategy:
-      matrix:
-        environment: ${{ fromJSON(needs.get_default_envs.outputs.environments) }}
-    steps:
-      - uses: actions/checkout@v3
-
-      - name: Get tags
-        run: git fetch --force --tags origin
-
-      - name: Cache pip
-        uses: actions/cache@v3
-        with:
-          path: ~/.cache/pip
-          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
-          restore-keys: |
-            ${{ runner.os }}-pip-
-
-      - name: Cache PlatformIO
-        uses: actions/cache@v3
-        with:
-          path: ~/.platformio
-          key: ${{ runner.os }}-${{ hashFiles('**/lockfiles') }}
-
-      - name: Set up Python
-        uses: actions/setup-python@v4
-        with:
-          python-version: "3.9"
-
-      - name: Install PlatformIO
-        run: |
-          python -m pip install --upgrade pip
-          pip install --upgrade platformio
-
-      - name: Setup Node.js and yarn
-        uses: actions/setup-node@v3
-        with:
-          node-version: "18"
-          cache: "yarn"
-          cache-dependency-path: "webapp/yarn.lock"
-
-      - name: Install WebApp dependencies
-        run: yarn --cwd webapp install --frozen-lockfile
-
-      - name: Build WebApp
-        run: yarn --cwd webapp build
-
-      - name: Build firmware
-        run: pio run -e ${{ matrix.environment }}
-
-      - name: Rename Firmware
-        run: mv .pio/build/${{ matrix.environment }}/firmware.bin .pio/build/${{ matrix.environment }}/opendtu-onbattery-${{ matrix.environment }}.bin
-
-      - name: Rename Factory Firmware
-        run: mv .pio/build/${{ matrix.environment }}/firmware.factory.bin .pio/build/${{ matrix.environment }}/opendtu-onbattery-${{ matrix.environment }}.factory.bin
-
-      - uses: actions/upload-artifact@v3
-        with:
-          name: opendtu-onbattery-${{ matrix.environment }}
-          path: |
-            .pio/build/${{ matrix.environment }}/opendtu-onbattery-${{ matrix.environment }}.bin
-            .pio/build/${{ matrix.environment }}/opendtu-onbattery-${{ matrix.environment }}.factory.bin
-
-