tests: make wait_for_all_mutations faster

Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>

tests/queries/0_stateless/mergetree_mutations.lib

@@ -29,7 +29,6 @@ function wait_for_all_mutations()
 
     for i in {1..200}
     do
-        sleep 1
         if [[ $(${CLICKHOUSE_CLIENT} --query="SELECT coalesce(minOrNull(is_done), 1) FROM system.mutations WHERE database='$database' AND table like '$table'") -eq 1 ]]; then
             break
         fi
@@ -38,6 +37,7 @@ function wait_for_all_mutations()
             echo "Timed out while waiting for mutation to execute!"
         fi
 
+        sleep 0.1
     done
 }