Revert "stop testing with broken upstream/version-2-0"

[tersec]

Reverts #6554

If upstream Nim has been fixed, can test version-2-0 again

[tersec]

still nope:

2024-09-21T03:25:59.6500018Z /github-runner/workspace/nimbus-eth2/nimbus-eth2/ncli/ncli_db.nim(781, 19) template/generic instantiation of `info` from here
2024-09-21T03:25:59.6501775Z /github-runner/workspace/nimbus-eth2/nimbus-eth2/ncli/ncli_db.nim(780, 32) Error: template instantiation too nested
2024-09-21T03:25:59.8078153Z make: *** [Makefile:447: ncli_db] Error 1

at least it's different than the first two version-2-0/nimbus-eth2 regressions

[github-actions]

Unit Test Results

         9 files  ±0    1 355 suites  ±0   39m 28s ⏱️ +38s
  5 149 tests ±0    4 801 ✔️ ±0  348 💤 ±0  0 ❌ ±0 
21 522 runs  ±0  21 118 ✔️ ±0  404 💤 ±0  0 ❌ ±0 

Results for commit 9a3b1f7. ± Comparison against base commit 256f6b8.

[tersec]

That one is arguably a not-great template in Nimbus, fixed by b7f3f0c but that allowed finding nim-lang/Nim#24150 in its place, which shows up as e.g., https://github.com/status-im/nimbus-eth2/actions/runs/10972715518/job/30469294056?pr=6573

2024-09-21T13:08:42.2537044Z /github-runner/workspace/nimbus-eth2/nimbus-eth2/tests/consensus_spec/phase0/test_fixture_operations.nim(97, 43) Error: request to generate code for .compileTime proc: preset