patch 8.0.1265: swap test not skipped when there is one group

Problem:    Swap test not skipped when there is one group.
Solution:   Convert list to string for the message.

src/testdir/test_swap.vim

@@ -53,7 +53,7 @@ func Test_swap_group()
   endif
   let groups = split(system('groups'))
   if len(groups) <= 1
-    throw 'Skipped: need at least two groups, got ' . groups
+    throw 'Skipped: need at least two groups, got ' . string(groups)
   endif
 
   call delete('Xtest')

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1265,
 /**/
     1264,
 /**/