Ignore warnings for shutdown taking too long (#2089)

Signed-off-by: Oriol Muñoz <oriol.munoz@digitalasset.com>

Author: OriolMunoz-da

project/ignore-patterns/canton_network_test_log.ignore.txt

@@ -86,6 +86,7 @@ unexpected exception: Task slick.*rejected from slick.util.AsyncExecutorWithMetr
 
 # TODO (#944): investigate what task is it still running and see if we can somehow fix it
 Timeout 10 seconds expired, but tasks still running. Shutting down forcibly
+ForkJoinIdlenessExecutorService.*shutdown did not complete gracefully in allotted
 
 Consensus not reached.*BftScanConnection:BftScanConnectionTest.*