build: set actions/setup-python to v2

This upgrades the `setup-python` action and pins it to the latest v2,
which suppresses the warnings about set-env and add-path:

    Error: The `set-env` command is deprecated and will be disabled on November 16th. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/

.github/workflows/superset-e2e.yml

@@ -33,7 +33,7 @@ jobs:
     - name: Checkout code
       uses: actions/checkout@v2
     - name: Setup Python
-      uses: actions/setup-python@v2.1.1
+      uses: actions/setup-python@v2
       with:
         python-version: '3.7'
     - name: OS dependencies

.github/workflows/superset-python.yml

@@ -13,7 +13,7 @@ jobs:
     - name: Checkout code
       uses: actions/checkout@v2
     - name: Setup Python
-      uses: actions/setup-python@v2.1.1
+      uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
@@ -36,7 +36,7 @@ jobs:
     - name: Checkout code
       uses: actions/checkout@v2
     - name: Setup Python
-      uses: actions/setup-python@v2.1.1
+      uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
@@ -58,7 +58,7 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v2
       - name: Setup Python
-        uses: actions/setup-python@v2.1.1
+        uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
@@ -111,7 +111,7 @@ jobs:
       steps:
       - uses: actions/checkout@v2
       - name: Setup Python
-        uses: actions/setup-python@v2.1.1
+        uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
@@ -168,7 +168,7 @@ jobs:
     - name: Start hadoop and hive
       run: docker-compose -f scripts/databases/hive/docker-compose.yml up -d
     - name: Setup Python
-      uses: actions/setup-python@v2.1.1
+      uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
@@ -216,7 +216,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: Setup Python
-      uses: actions/setup-python@v2.1.1
+      uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
@@ -262,7 +262,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: Setup Python
-      uses: actions/setup-python@v2.1.1
+      uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
@@ -301,7 +301,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: Setup Python
-      uses: actions/setup-python@v2.1.1
+      uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies

.github/workflows/superset-translations.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v2
       - name: Setup Python
-        uses: actions/setup-python@v2.1.1
+        uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies

.github/workflows/test-hive.yml

@@ -40,7 +40,7 @@ jobs:
     - name: Start hadoop and hive
       run: docker-compose -f scripts/databases/hive/docker-compose.yml up -d
     - name: Setup Python
-      uses: actions/setup-python@v2.1.1
+      uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies

.github/workflows/test-presto.yml

@@ -43,7 +43,7 @@ jobs:
       steps:
       - uses: actions/checkout@v2
       - name: Setup Python
-        uses: actions/setup-python@v2.1.1
+        uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies