'+' still replaced by `\u002B`

[ixje]

Describe the bug https://github.com/neo-project/neo/pull/2307 was closed as a duplicate of https://github.com/neo-project/neo/pull/2050 while the latter was also closed without ever including the fix. I ran into a state (and gas consumption) issue with testnet block 398890 where a JSON string was stored and the + was replaced by \u002B. + is a valid base64 character so we're unnecessary increasing storage size and cost for users.

Expected behavior + in a base64 encoded string should stay a +.

Platform:

• Version neo-cli 3.0.3