Stop running London / Paris / Shanghai `BlockChainReferenceTest`

[OlivierBBB]

At some point ...

[amkCha]

From Prague and on, we are dowloading fixtures (ref tests) from the ethereum repo

As soon as we are not expected to support London through Cancun forks

• remove the submodule linea-tracer/reference-tests/src/test/resources/ethereum-tests
• the associated gradle tasks
• the CI flows