Pending fix of Unit test in electra

[rodrigo-o]

Right now we have 4 unit test not yet running, they were marked as :skip in #1400.

*Note: The first one is tracked in a separate issue #1407 *

  2) test stacktrace encode nested container (Unit.SSZExTest)
     test/unit/ssz_ex_test.exs:897
     ** (MatchError) no match of right hand side value: {:ok, <<8, 0, 0, 0, 252, 0, 0, 0, 228, 0, 0, 0, 218, 138, 84, 194, 236, 27, 46, 70, 218, 202, 156, 184, 220, 22, 12, 96, 31, 38, 101, 174, 248, 168, 116, 226, 15, 39, 218, 148, 42, 8, 80, 80, 241, 149, 162, 32, ...>>}
     code: {:error, error} = SszEx.encode(attester_slashing)
     stacktrace:
       test/unit/ssz_ex_test.exs:900: (test)

................

  3) test stacktrace hash_tree_root nested container (Unit.SSZExTest)
     test/unit/ssz_ex_test.exs:906
     ** (MatchError) no match of right hand side value: {:ok, <<75, 101, 47, 45, 63, 59, 207, 75, 12, 215, 6, 90, 105, 103, 204, 81, 54, 83, 22, 63, 79, 194, 69, 52, 34, 34, 51, 16, 104, 92, 101, 165>>}
     code: {:error, error} = SszEx.hash_tree_root(attester_slashing)
     stacktrace:
       test/unit/ssz_ex_test.exs:908: (test)

......................................................................................................
15:41:55.340 [error] [BlockDb] Error pruning blocks: :invalid_iterator
...........................................

  4) test Calculating all committees for a single epoch should be the same by any method (Unit.StateTransition.MiscTest)
     test/unit/state_transition/misc_test.exs:15
     Assertion with == failed
     code:  assert Diff.diff(adapted_committees, all_committees_individual) == :unchanged
     left:  %{added_right: [error: "Empty indices", error: "Empty indices", error: "Empty indices", error: "Empty indices", error: "Empty indices", error: "Empty indices", error: "Empty indices", error: "Empty indices"]}
     right: :unchanged
     stacktrace:
       test/unit/state_transition/misc_test.exs:20: (test)