tests: remove EnsureLoaded

This should not be necessary in general, and causes e.g. :FZF to be
loaded from the global Vim runtime (causing an assertion failure in the
tests).

It is replaced by a verbatim / trimmed down `:runtime` for the "Check
installed plugins" test.

test/test.vader

@@ -44,12 +44,6 @@ Execute (Initialize test environment):
   endfunction
   command! -nargs=+ -bang AssertExpect call AssertExpect('<bang>' == '!', <args>)
 
-  function! EnsureLoaded()
-    if has('vim_starting')
-      runtime! plugin/**/*.vim
-    endif
-  endfunction
-
   function! RmRf(file)
     call system(printf('rm -rf "%s"', a:file))
   endfunction
@@ -98,7 +92,6 @@ Execute (Cleanup):
   silent! delf PlugStatusSorted
   silent! delf AssertExpect
   silent! delf PlugUpdated
-  silent! delf EnsureLoaded
   silent! delf ReloadPlug
   silent! delc AssertExpect
   silent! unmap /

test/workflow.vader

@@ -582,7 +582,7 @@ Given (Unaligned code):
   aa=2
 
 Execute (Check installed plugins):
-  call EnsureLoaded()
+  runtime plugin/fnr.vim plugin/redis.vim
   Assert exists(':FNR'),           'FNR command should be found'
   Assert !exists(':RedisExecute'), 'RedisExecute command still should not be found'
 
@@ -1341,7 +1341,6 @@ Execute (Strict load order):
   Plug '$PLUG_FIXTURES/xxx'
   Plug '$PLUG_FIXTURES/yyy', { 'for': ['xxx'] }
   call plug#end()
-  call EnsureLoaded()
   setf xxx
   Log 'Case 1: ' . &rtp
   AssertEqual ['yyy/ftdetect', 'yyy/after/ftdetect', 'xxx/ftdetect', 'xxx/after/ftdetect'], g:total_order[0:3]
@@ -1355,7 +1354,6 @@ Execute (Strict load order):
   Plug '$PLUG_FIXTURES/xxx', { 'for': ['xxx'] }
   Plug '$PLUG_FIXTURES/yyy'
   call plug#end()
-  call EnsureLoaded()
   set rtp^=manually-prepended
   set rtp+=manually-appended
   setf xxx
@@ -1375,7 +1373,6 @@ Execute (Strict load order):
   Plug '$PLUG_FIXTURES/xxx', { 'for': ['xxx'] }
   Plug '$PLUG_FIXTURES/yyy', { 'for': ['xxx'] }
   call plug#end()
-  call EnsureLoaded()
   setf xxx
   Log 'Case 3: ' . &rtp
   AssertEqual ['xxx/ftdetect', 'xxx/after/ftdetect', 'yyy/ftdetect', 'yyy/after/ftdetect'], g:total_order[0:3]