patch 8.1.1079: no need for a separate ScreenLinesUtf8() test function

Problem:    No need for a separate ScreenLinesUtf8() test function.
Solution:   Get the composing characters with ScreenLines().
diff --git a/src/testdir/view_util.vim b/src/testdir/view_util.vim
index 34b4519..cb861bc 100644
--- a/src/testdir/view_util.vim
+++ b/src/testdir/view_util.vim
@@ -5,29 +5,10 @@
   finish
 endif
 
-" Get text on the screen, without composing characters.
-" ScreenLines(lnum, width) or
-" ScreenLines([start, end], width)
-function! ScreenLines(lnum, width) abort
-  redraw!
-  if type(a:lnum) == v:t_list
-    let start = a:lnum[0]
-    let end = a:lnum[1]
-  else
-    let start = a:lnum
-    let end = a:lnum
-  endif
-  let lines = []
-  for l in range(start, end)
-    let lines += [join(map(range(1, a:width), 'nr2char(screenchar(l, v:val))'), '')]
-  endfor
-  return lines
-endfunction
-
 " Get text on the screen, including composing characters.
 " ScreenLines(lnum, width) or
 " ScreenLines([start, end], width)
-function! ScreenLinesUtf8(lnum, width) abort
+function! ScreenLines(lnum, width) abort
   redraw!
   if type(a:lnum) == v:t_list
     let start = a:lnum[0]