fix: added versions for python envs

Author: savon-noir

.github/workflows/preflight_check.yaml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8]
+        python-version: [3.6.15, 3.7.17, 3.8.18]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}
@@ -37,7 +37,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [2.7, 3.5, 3.6, 3.7, 3.8]
+        python-version: [3.5.10, 3.6.15, 3.7.17, 3.8.18]
     steps:
     - uses: actions/checkout@v2
     - name: Setup Python ${{ matrix.python-version }}