Remove pip cache from Action

.github/workflows/unit-tests.yml

@@ -18,18 +18,6 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-    - name: Cache pip
-      uses: actions/cache@v2
-      with:
-        path: ~/.cache/pip
-        key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
-        restore-keys: |
-          ${{ runner.os }}-pip-
-    - name: Cache PlatformIO
-      uses: actions/cache@v2
-      with:
-        path: ~/.platformio
-        key: ${{ runner.os }}-${{ hashFiles('**/lockfiles') }}
 
     - name: Set up Python
       uses: actions/setup-python@v2