Remove "highbright bold" conversion. Fixes #11190

When using TUI host terminal should take care of this (regardless
if 'termguicolors' is active or not). For GUI the behavior doesn't make
sense (GUI should display bold attr as bold always).

(cherry picked from commit b772b86d2b)

src/nvim/terminal.c

@@ -220,8 +220,6 @@ Terminal *terminal_open(TerminalOptions opts)
   rv->sb_size = (size_t)curbuf->b_p_scbk;
   rv->sb_buffer = xmalloc(sizeof(ScrollbackLine *) * rv->sb_size);
 
-  vterm_state_set_bold_highbright(state, true);
-
   // Configure the color palette. Try to get the color from:
   //
   // - b:terminal_color_{NUM}