docs: re-order when to download test data

This probably needs to happend before actually running any tests.

docs/community/contribute/02_workflow.md

@@ -25,6 +25,12 @@ pytest -m core
     or any specific backends (`ibis/backends`) this material isn't necessary to
     follow to make a pull request.
 
+First, we need to download example data to run the tests successfully:
+
+```sh
+just download-data
+```
+
 To run the tests for a specific backend (e.g. sqlite):
 
 ```sh
@@ -50,14 +56,6 @@ export PGPASSWORD=postgres
 psql -t -A -h localhost -U postgres -d ibis_testing -c "select 'success'"
 ```
 
-## Download Test Data
-
-Backends need to be populated with test data to run the tests successfully:
-
-```sh
-just download-data
-```
-
 ## Writing the commit
 
 Ibis follows the [Conventional Commits](https://www.conventionalcommits.org/) structure.