patch 9.1.1409: using f-flag in 'complete' conflicts with Neovim

Problem:  using f-flag in 'complete' conflicts with Neovims filename
          completion (glepnir, after v9.1.1301).
Solution: use upper-case "F" flag for completion functions
          (Girish Palya).

fixes: #17347
closes: #17378

Signed-off-by: Girish Palya <girishji@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/insexpand.c b/src/insexpand.c
index c7d6fd4..700f734 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -4091,7 +4091,7 @@
 	    }
 	}
 #ifdef FEAT_COMPL_FUNC
-	else if (*st->e_cpt == 'f' || *st->e_cpt == 'o')
+	else if (*st->e_cpt == 'F' || *st->e_cpt == 'o')
 	{
 	    compl_type = CTRL_X_FUNCTION;
 	    if (*st->e_cpt == 'o')
@@ -6916,7 +6916,7 @@
 	{
 	    if (*p == 'o')
 		cb = &curbuf->b_ofu_cb;
-	    else if (*p == 'f')
+	    else if (*p == 'F')
 		cb = (*(p + 1) != ',' && *(p + 1) != NUL)
 		    ? get_cpt_func_callback(p + 1) : &curbuf->b_cfu_cb;
 	    if (cb)