Fix pyarrow test (apache#4450)

* Rollback ubuntu version

* Remove file

Author: mvanschellebeeck

.github/workflows/rust.yml

@@ -234,7 +234,7 @@ jobs:
 
   test-datafusion-pyarrow:
     needs: [linux-build-lib]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         arch: [amd64]