Remove workflows 3.7 CI testing

3.7 no longer is available on github workflows

Author: rocky

.github/workflows/osx.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         os: [macOS]
-        python-version: [3.7, 3.8]
+        python-version: [3.8]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}

.github/workflows/ubuntu.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.7, 3.8]
+        python-version: [3.8]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}

.github/workflows/windows.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         os: [windows]
-        python-version: [3.7, 3.8]
+        python-version: [3.8]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}