Update TS test matrix to drop 3.9 and add 4.4/4.5

Author: markerikson

.github/workflows/test.yml

@@ -40,7 +40,7 @@ jobs:
       fail-fast: false
       matrix:
         node: ['14.x']
-        ts: ['3.9', '4.0', '4.1', '4.2', '4.3', 'next']
+        ts: ['4.0', '4.1', '4.2', '4.3', '4.4', '4.5', 'next']
     steps:
       - name: Checkout repo
         uses: actions/checkout@v2