patch 8.1.1330: using bold attribute in terminal changes the color

Problem:    Using bold attribute in terminal changes the color. (Jason
            Franklin)
Solution:   Don't set the "bold-highbright" flag in vterm unless the terminal
            supports less than 16 colors.
diff --git a/src/terminal.c b/src/terminal.c
index bc57d64..caa4c85 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -3976,7 +3976,9 @@
 	    &term->tl_default_color.fg,
 	    &term->tl_default_color.bg);
 
-    if (t_colors >= 16)
+    if (t_colors < 16)
+	// Less than 16 colors: assume that bold means using a bright color for
+	// the foreground color.
 	vterm_state_set_bold_highbright(vterm_obtain_state(vterm), 1);
 
     /* Required to initialize most things. */