Update tests.yaml

Author: alex2211-put

.github/workflows/tests.yaml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.8]
+        python-version: [3.7]
         environment: [py, py-tls, py-proto3, py-tls-proto3]
         folder: [ydb, tests]
         exclude: