this should fix 3.10 being interpreted as 3.1

Author: DanielGoldfarb

.github/workflows/mplfinance_checks.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.8, 3.9, 3.10 ]
+        python-version: ['3.8', '3.9', '3.10' ]
     steps:
       - name: Preliminary Information
         run: |