chore: update GitHub Actions workflow to install Poetry and dependencies, removing MPM checkout steps

.github/workflows/custom_build.yml

@@ -116,29 +116,17 @@ jobs:
           cd firmware
           git apply ../meshforge/firmware-patch.diff
 
-      - name: Update Status - Fetching Mesh Package Manager
+      - name: Update Status - Installing Poetry & Dependencies
         shell: bash
         run: |
           source /tmp/update_status.sh
-          update_status checking_out_mpm
+          update_status installing_poetry_dependencies
 
-      - name: Checkout Mesh Package Manager
-        uses: actions/checkout@v4
-        with:
-          repository: MeshEnvy/mpm
-          path: mpm
-          fetch-depth: 1
-
-      - name: Update Status - Fetching Mesh Package Manager
-        shell: bash
-        run: |
-          source /tmp/update_status.sh
-          update_status checking_out_mpm
-
-      - name: Install Python Requirements
+      - name: Install Poetry & Dependencies
         working-directory: firmware
         run: |
           pip install poetry
+          poetry config virtualenvs.in-project true
           poetry install
 
       - name: Update Status - Installing plugins
@@ -181,7 +169,6 @@ jobs:
           python -m pip install --upgrade pip
           pip install platformio
 
-
       - name: Update Status - Building Firmware
         shell: bash
         run: |