Remove ESP32 CI

Will be replaced by MicroPython's CI scripts.

.github/workflows/esp32_port.yml

@@ -1,37 +0,0 @@
-name: Build lv_micropython esp32 port
-
-on:
-  push:
-    branches: [ master ]
-  pull_request:
-    branches: [ master ]
-
-jobs:
-  build:
-    runs-on: ubuntu-18.04
-    strategy:
-      matrix:
-        board: [GENERIC_SPIRAM]
-    steps:
-    - uses: actions/checkout@v2
-    - name: Install ESPIDF
-      run: | 
-        git clone https://github.com/espressif/esp-idf.git
-        git -C esp-idf checkout v4.0.2
-        git -C esp-idf submodule update --init components/bt/controller/lib components/bt/host/nimble/nimble components/esp_wifi/lib_esp32 components/esptool_py/esptool components/lwip/lwip components/mbedtls/mbedtls
-        ./esp-idf/install.sh
-    - name: Set ESPIDF path
-      run: echo "ESPIDF=$PWD/esp-idf" >> $GITHUB_ENV
-    - name: Update submodules
-      run: git submodule update --init --recursive  
-    - name: Build mpy-cross
-      run: make -j $(nproc) -C mpy-cross
-    - name: Build ${{ matrix.board }}
-      run: |
-        source esp-idf/export.sh
-        make -j $(nproc) -C ports/esp32 BOARD=${{ matrix.board }} LV_CFLAGS="-DLV_COLOR_DEPTH=16 -DLV_COLOR_16_SWAP=1"
-    - uses: actions/upload-artifact@v2
-      if: ${{ env.GITHUB_EVENT_NAME }} == 'push'
-      with:
-        name: ${{ matrix.board }}.hex
-        path: ports/esp32/build-${{ matrix.board }}/firmware.hex