eth/tracers: fix test

[rjl493456442]

This pull request fixes a broken unit test

=== CONT  TestTracingWithOverrides
    api_test.go:1012: result: {"gas":21167,"failed":false,"returnValue":"0x0000000000000000000000000000000000000000000000000000000000000002","structLogs":[{"pc":0,"op":"PUSH1","gas":24978860,"gasCost":3,"depth":1,"stack":[]},{"pc":2,"op":"CALLDATALOAD","gas":24978857,"gasCost":3,"depth":1,"stack":["0x0"]},{"pc":3,"op":"PUSH1","gas":24978854,"gasCost":3,"depth":1,"stack":["0x1"]},{"pc":5,"op":"ADD","gas":24978851,"gasCost":3,"depth":1,"stack":["0x1","0x1"]},{"pc":6,"op":"PUSH1","gas":24978848,"gasCost":3,"depth":1,"stack":["0x2"]},{"pc":8,"op":"MSTORE","gas":24978845,"gasCost":6,"depth":1,"stack":["0x2","0x0"]},{"pc":9,"op":"PUSH1","gas":24978839,"gasCost":3,"depth":1,"stack":[]},{"pc":11,"op":"PUSH1","gas":24978836,"gasCost":3,"depth":1,"stack":["0x20"]},{"pc":13,"op":"RETURN","gas":24978833,"gasCost":0,"depth":1,"stack":["0x20","0x0"]}]}
    api_test.go:1013: test 10, result mismatch, have
        {21167 false 0x0000000000000000000000000000000000000000000000000000000000000002}
        , want
        {21167 false 0000000000000000000000000000000000000000000000000000000000000002}
    api_test.go:1012: result: {"gas":25664,"failed":false,"returnValue":"0x000000000000000000000000c6e93f4c1920eaeaa1e699f76a7a8c18e3056074","structLogs":[]}
    api_test.go:1013: test 11, result mismatch, have
        {25664 false 0x000000000000000000000000c6e93f4c1920eaeaa1e699f76a7a8c18e3056074}
        , want
        {25664 false 000000000000000000000000c6e93f4c1920eaeaa1e699f76a7a8c18e3056074}