test: remove use of require('test.helpers')

The test.functional.helpers and test.unit.helpers modules now include
all of the public functions from test.helpers, so there is no need to
separately require('test.helpers').

test/functional/ui/options_spec.lua

@@ -1,10 +1,9 @@
-local global_helpers = require('test.helpers')
 local helpers = require('test.functional.helpers')(after_each)
 local Screen = require('test.functional.ui.screen')
 local clear = helpers.clear
 local command = helpers.command
 local eq = helpers.eq
-local shallowcopy = global_helpers.shallowcopy
+local shallowcopy = helpers.shallowcopy
 
 describe('ui receives option updates', function()
   local screen

test/functional/ui/screen.lua

@@ -71,11 +71,10 @@
 -- To help write screen tests, see Screen:snapshot_util().
 -- To debug screen tests, see Screen:redraw_debug().
 
-local global_helpers = require('test.helpers')
-local deepcopy = global_helpers.deepcopy
-local shallowcopy = global_helpers.shallowcopy
-local concat_tables = global_helpers.concat_tables
 local helpers = require('test.functional.helpers')(nil)
+local deepcopy = helpers.deepcopy
+local shallowcopy = helpers.shallowcopy
+local concat_tables = helpers.concat_tables
 local request, run_session = helpers.request, helpers.run_session
 local eq = helpers.eq
 local dedent = helpers.dedent

test/functional/ui/wildmode_spec.lua

@@ -1,7 +1,6 @@
-local global_helpers = require('test.helpers')
-local shallowcopy = global_helpers.shallowcopy
 local helpers = require('test.functional.helpers')(after_each)
 local Screen = require('test.functional.ui.screen')
+local shallowcopy = helpers.shallowcopy
 local clear, feed, command = helpers.clear, helpers.feed, helpers.command
 local iswin = helpers.iswin
 local funcs = helpers.funcs