fix(tests): EIP-6110: Add slow marker to many_deposits test

Author: marioevz

tests/prague/eip6110_deposits/test_deposits.py

@@ -301,6 +301,7 @@
                 ),
             ],
             id="many_deposits_from_contract",
+            marks=pytest.mark.slow,
         ),
         pytest.param(
             [
@@ -472,6 +473,7 @@
                 ),
             ],
             id="many_deposits_from_contract_oog",
+            marks=pytest.mark.slow,
         ),
         pytest.param(
             [