patch 8.2.1314: Vim9: rule for comment after :function is confusing

Problem:    Vim9: rule for comment after :function is confusing.
Solution:   Allow double quoted comment after :function in vim9script.
            (closes #6556)
diff --git a/src/userfunc.c b/src/userfunc.c
index d17e807..343c9cd 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -2832,7 +2832,8 @@
     if (*p == '\n')
 	line_arg = p + 1;
     else if (*p != NUL
-	    && !(*p == '"' && !(vim9script || eap->cmdidx == CMD_def))
+	    && !(*p == '"' && (!vim9script || eap->cmdidx == CMD_function)
+						     && eap->cmdidx != CMD_def)
 	    && !(*p == '#' && (vim9script || eap->cmdidx == CMD_def))
 	    && !eap->skip
 	    && !did_emsg)