CI: Use CrateDB nightly also for regular testing

Author: amotl

.github/workflows/tests.yml

@@ -19,7 +19,7 @@ jobs:
       matrix:
         os: ['ubuntu-latest', 'macos-latest']
         python-version: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
-        cratedb-version: ['5.7.2']
+        cratedb-version: ['nightly']
 
         # To save resources, only use the most recent Python versions on macOS.
         exclude: