patch 9.1.0831: 'findexpr' can't be used as lambad or Funcref

Problem:  'findexpr' can't be used for lambads
          (Justin Keyes)
Solution: Replace the findexpr option with the findfunc option
          (Yegappan Lakshmanan)

related: #15905
closes: #15976

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/buffer.c b/src/buffer.c
index f1e1330..3b05f25 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2412,7 +2412,6 @@
     clear_string_option(&buf->b_p_fp);
 #if defined(FEAT_EVAL)
     clear_string_option(&buf->b_p_fex);
-    clear_string_option(&buf->b_p_fexpr);
 #endif
 #ifdef FEAT_CRYPT
 # ifdef FEAT_SODIUM
@@ -2485,6 +2484,8 @@
 #ifdef FEAT_EVAL
     clear_string_option(&buf->b_p_tfu);
     free_callback(&buf->b_tfu_cb);
+    clear_string_option(&buf->b_p_ffu);
+    free_callback(&buf->b_ffu_cb);
 #endif
     clear_string_option(&buf->b_p_dict);
     clear_string_option(&buf->b_p_tsr);