test: Update to py3.9 (#808)

Author: pgrzesik

.github/workflows/validate.yml

@@ -43,10 +43,10 @@ jobs:
             npm-v18-${{ runner.os }}-${{ github.ref }}-
             npm-v18-${{ runner.os }}-refs/heads/master-
 
-      - name: Set up Python 3.7
+      - name: Set up Python 3.9
         uses: actions/setup-python@v2
         with:
-          python-version: 3.7
+          python-version: 3.9
 
       - name: Install Node.js and npm
         uses: actions/setup-node@v1

example/serverless.yml

@@ -2,7 +2,7 @@ service: sls-py-req-test
 
 provider:
   name: aws
-  runtime: python3.7
+  runtime: python3.9
 
 plugins:
   - serverless-python-requirements

example_native_deps/serverless.yml

@@ -2,7 +2,7 @@ service: sls-py-req-test
 
 provider:
   name: aws
-  runtime: python3.7
+  runtime: python3.9
 
 plugins:
   - serverless-python-requirements