remove: Cache pip in CI workflow

Author: shima004

.github/workflows/ci.yaml

@@ -22,14 +22,6 @@ jobs:
         with:
           python-version: 3.12
 
-      - name: Cache pip
-        uses: actions/cache@v4
-        with:
-          path: ~/.cache/pip
-          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
-          restore-keys: |
-            ${{ runner.os }}-pip-
-
       - name: Cache virtual environment
         uses: actions/cache@v4
         with: