patch 9.0.1242: code for :runtime completion is not consistent

Problem:    Code for :runtime completion is not consistent.
Solution:   Make code for cmdline expansion more consistent. (closes #11875)
diff --git a/src/testdir/test_packadd.vim b/src/testdir/test_packadd.vim
index 332f009..89b7817 100644
--- a/src/testdir/test_packadd.vim
+++ b/src/testdir/test_packadd.vim
@@ -27,7 +27,7 @@
 
   let rtp_entries = split(rtp, ',')
   for entry in rtp_entries
-    if entry =~? '\<after\>' 
+    if entry =~? '\<after\>'
       let first_after_entry = entry
       break
     endif
@@ -183,7 +183,7 @@
   exec "silent !rmdir" top2_dir
 endfunc
 
-" Check command-line completion for 'packadd'
+" Check command-line completion for :packadd
 func Test_packadd_completion()
   let optdir1 = &packpath . '/pack/mine/opt'
   let optdir2 = &packpath . '/pack/candidate/opt'
@@ -271,9 +271,9 @@
 
   helptags ALL
 
-  let tags1 = readfile(docdir1 . '/tags') 
+  let tags1 = readfile(docdir1 . '/tags')
   call assert_match('look-here', tags1[0])
-  let tags2 = readfile(docdir2 . '/tags') 
+  let tags2 = readfile(docdir2 . '/tags')
   call assert_match('look-away', tags2[0])
 
   call assert_fails('helptags abcxyz', 'E150:')