fixup(forks): Return instead of error raise in blob_gas_per_blob

Author: marioevz

src/ethereum_test_forks/forks/forks.py

@@ -259,7 +259,7 @@ def blob_gas_per_blob(cls, block_number: int = 0, timestamp: int = 0) -> int:
         """
         Returns the amount of blob gas used per blob at a given fork.
         """
-        raise NotImplementedError("Blob gas per blob is not supported in Frontier")
+        return 0
 
     @classmethod
     def target_blobs_per_block(cls, block_number: int = 0, timestamp: int = 0) -> int: