apacheGH-39880: [Python][CI] Pin moto<5 for dask integration tests (a…

…pache#39881)

See upstream pin being added (dask/dask#10868 / dask/dask#10869), we are seeing the same failures
* Closes: apache#39880

Lead-authored-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>
Co-authored-by: Raúl Cumplido <raulcumplido@gmail.com>
Signed-off-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>

ci/scripts/install_dask.sh

@@ -35,4 +35,5 @@ else
 fi
 
 # additional dependencies needed for dask's s3 tests
-pip install moto[server] flask requests
+# Moto 5 results in timeouts in s3 tests: https://github.com/dask/dask/issues/10869
+pip install "moto[server]<5" flask requests