patch 8.1.0026: terminal test fails with very tall terminal

Problem:    Terminal test fails with very tall terminal. (Tom)
Solution:   Fix the terminal window size in the test.

src/testdir/test_terminal.vim

@@ -270,7 +270,7 @@ func Test_terminal_scroll()
 endfunc
 
 func Test_terminal_scrollback()
-  let buf = Run_shell_in_terminal({})
+  let buf = Run_shell_in_terminal({'term_rows': 15})
   set termwinscroll=100
   call writefile(range(150), 'Xtext')
   if has('win32')

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    26,
 /**/
     25,
 /**/