patch 9.1.0268: Two tests in test_filechanged.vim are slow

Problem:  Two tests in test_filechanged.vim are slow.
Solution: Sleep for shorter if the +nanotime feature is available.
          (zeertzjq)

closes: #14418

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 5534b9b..cf57e38 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    268,
+/**/
     267,
 /**/
     266,