Update test to use updated nightly URL

Author: rfay

.github/workflows/tests.yml

@@ -18,6 +18,9 @@ defaults:
   run:
     shell: bash
 
+env:
+  NIGHTLY_DDEV_PR_URL: "https://nightly.link/drud/ddev/actions/artifacts/146117649.zip"
+
 jobs:
   tests:
     defaults:
@@ -54,7 +57,7 @@ jobs:
     - name: Use ddev PR
       if: matrix.ddev_version == 'PR'
       run: |
-        curl -sSL -o ddev_linux.zip https://nightly.link/drud/ddev/actions/artifacts/144791287.zip
+        curl -sSL -o ddev_linux.zip ${NIGHTLY_DDEV_PR_URL}
         unzip ddev_linux.zip
         mv ddev /usr/local/bin/ddev && chmod +x /usr/local/bin/ddev