Don't set the oper flags on client

[glguy]

The oper_conf flags are a different set of flag
bits than the client flags. The oper flags are
hardcoded to have ENCRYPTED set which is the same
flag as PINGSENT on the client struct. This can
cause a client to timeout if the last thing it
does is oper up.

[ilbelkyr]

It looks like this was a remnant of a mechanism to apply privileges directly from the operator blocks which was deprecated with the introduction of privsets and removed in 10847f6. The deoper code still makes sure to remove oper-only flags:

solanum/include/s_newconf.h

Line 143 in 4e89f66

#define OPER_FLAGS 0 /* no oper privs in Client.flags/oper_conf.flags currently */

solanum/ircd/s_user.c

Line 1180 in 4e89f66

source_p->flags &= ~OPER_FLAGS;

We can probably remove those lines as well considering they've gone unused since 2008.