[CI] Changed tested python version to 3.7 and 3.10

We cannot add python 3.6 because there is no precompiled version of it to used.
Therefor, will be using 3.7 as the minimum version in CI.
In addition, dropped version limits from pytest.

.github/workflows/ci.yml

@@ -10,6 +10,9 @@ on:
 jobs:
   test-linux:
     runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        python-version: ["3.7", "3.10"]
 
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
@@ -20,7 +23,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.8"
+          python-version: ${{ matrix.python-version }}
 
       - name: Cache pip
         uses: actions/cache@v2
@@ -81,6 +84,9 @@ jobs:
 
   test-windows:
     runs-on: windows-latest
+    strategy:
+      matrix:
+        python-version: ["3.7", "3.10"]
 
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
@@ -91,7 +97,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.8"
+          python-version: ${{ matrix.python-version }}
 
       - name: Cache pip
         uses: actions/cache@v2

requirements-tests.txt

@@ -1,4 +1,4 @@
-pytest != 5.2.3, < 5.4
+pytest
 pytest-twisted
 pytest-cov
 mock