Update tzdata to 2020.3 (GH-22856)

pganssle · web-flow · commit 9a1ad2cf02e5 · 2020-10-21T06:40:43.000-07:00
TBH I had forgotten that we pin this 😅, and it's been updated quite a few times since we added this.
diff --git a/Misc/requirements-test.txt b/Misc/requirements-test.txt
@@ -1 +1 @@
-tzdata==2020.1rc0
+tzdata==2020.3
