patch 9.1.0187: filetype: no support for Dafny files

Problem:  Dafny files are not recognized.
Solution: Recognize *.dfy files as filetype "dafny" (zeertzjq).

Ref: https://dafny.org/
Ref: https://github.com/mlr-msft/vim-loves-dafny

closes: #14226

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    187,
 /**/
     186,
 /**/