Fix bitop test failing because of old api

[ytkimirti]

Old rest api probably returned the binary result even thought it was invalid utf8. Hence the old code

assert await response.text() == r'{"result":"\x9e\x9d\x9c\x9b"}'

Currently if base64 encoding is not set, it returns � (replacement character), so the test fails.

[mdumandag]

I think we can remove this check altogether (starting from line 57 to 68). This is a client library, and it should not bother with the internal representation of the commands. It should just check if the commands are working.