Bump actions/cache from 2.1.5 to 2.1.6

Bumps [actions/cache](https://github.com/actions/cache) from 2.1.5 to 2.1.6.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](actions/cache@v2.1.5...v2.1.6)

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/py-dead-code.yml

@@ -20,7 +20,7 @@ jobs:
           python-version: '3.8'
 
       - name: "Cache pip"
-        uses: actions/cache@v2.1.5
+        uses: actions/cache@v2.1.6
         with:
           # This path is specific to Ubuntu
           path: ~/.cache/pip

.github/workflows/py-test.yml

@@ -28,7 +28,7 @@ jobs:
           python-version: '3.8'
 
       - name: "Cache pip"
-        uses: actions/cache@v2.1.5
+        uses: actions/cache@v2.1.6
         with:
           # This path is specific to Ubuntu
           path: ~/.cache/pip
@@ -82,7 +82,7 @@ jobs:
           python-version: ${{ matrix.python-version }}
 
       - name: "Cache pip"
-        uses: actions/cache@v2.1.5
+        uses: actions/cache@v2.1.6
         with:
           # This path is specific to Ubuntu
           path: ~/.cache/pip

.github/workflows/release.yml

@@ -62,7 +62,7 @@ jobs:
           python-version: 3.9
 
       - name: "Cache pip"
-        uses: actions/cache@v2.1.5
+        uses: actions/cache@v2.1.6
         with:
           # This path is specific to Ubuntu
           path: ~/.cache/pip