patch 9.0.0626: too many delete() calls in tests

Problem:    Too many delete() calls in tests.
Solution:   Use deferred delete where possible.
diff --git a/src/testdir/test_match.vim b/src/testdir/test_match.vim
index 8be5bc0..1896158 100644
--- a/src/testdir/test_match.vim
+++ b/src/testdir/test_match.vim
@@ -372,12 +372,11 @@
     call printf('%s]%s', repeat('x', 50), repeat('x', 70))->setline(1)
     call matchaddpos('ErrorMsg', [[1, 51]])
   END
-  call writefile(lines, 'XscriptMatchLinebreak')
+  call writefile(lines, 'XscriptMatchLinebreak', 'D')
   let buf = RunVimInTerminal('-S XscriptMatchLinebreak', #{rows: 10})
   call VerifyScreenDump(buf, 'Test_match_linebreak', {})
 
   call StopVimInTerminal(buf)
-  call delete('XscriptMatchLinebreak')
 endfunc
 
 func Test_match_with_incsearch()
@@ -388,7 +387,7 @@
     call setline(1, range(20))
     call matchaddpos('ErrorMsg', [3])
   END
-  call writefile(lines, 'XmatchWithIncsearch')
+  call writefile(lines, 'XmatchWithIncsearch', 'D')
   let buf = RunVimInTerminal('-S XmatchWithIncsearch', #{rows: 6})
   call VerifyScreenDump(buf, 'Test_match_with_incsearch_1', {})
 
@@ -397,7 +396,6 @@
 
   call term_sendkeys(buf, "\<CR>")
   call StopVimInTerminal(buf)
-  call delete('XmatchWithIncsearch')
 endfunc
 
 " Test for deleting matches outside of the screen redraw top/bottom lines
@@ -428,12 +426,11 @@
     call setline(1, "\tix")
     call matchadd('ErrorMsg', '\t')
   END
-  call writefile(lines, 'XscriptMatchTabLinebreak')
+  call writefile(lines, 'XscriptMatchTabLinebreak', 'D')
   let buf = RunVimInTerminal('-S XscriptMatchTabLinebreak', #{rows: 10})
   call VerifyScreenDump(buf, 'Test_match_tab_linebreak', {})
 
   call StopVimInTerminal(buf)
-  call delete('XscriptMatchTabLinebreak')
 endfunc