Remove SET NAMES usage which is no-op in SingleStore

[pmishchenko-ua]

No description provided.

[vocheretnyi-memsql]

I'm just wondering about this comment, this means, that the user should change it globally manually, before calling this function, right?

[pmishchenko-ua]

I've updated the comment, please check.
We also need @kesmit13 opinion on this behavior. Maybe we should catch the error and print a warning instead, but ignoring it could lead to weird errors I guess - e.g when the user sets charset=utf8mb4 in connect(), and then tries to write 4-byte symbols to utf8(mb3) tables

[kesmit13]

Does this change work in SingleStoreDB before 8.7? If not, we need to put in some sort of conditional to only do this change for that version. We can't break compatibility with older server versions.

[pmishchenko-ua]

Does this change work in SingleStoreDB before 8.7? If not, we need to put in some sort of conditional to only do this change for that version. We can't break compatibility with older server versions.

@kesmit13 This change does not depend on 8.7, as these variables have been introduced a while ago. Prior to 8.7, utf8mb4 was not the default database charset, so setting the session character set to utf8mb4 would require changing it on the server first.