test: remove the pipe created by new_pipename() (#26173)

test/functional/helpers.lua

@@ -869,6 +869,9 @@ function module.new_pipename()
   -- HACK: Start a server temporarily, get the name, then stop it.
   local pipename = module.eval('serverstart()')
   module.funcs.serverstop(pipename)
+  -- Remove the pipe so that trying to connect to it without a server listening
+  -- will be an error instead of a hang.
+  os.remove(pipename)
   return pipename
 end
 

test/functional/ui/embed_spec.lua

@@ -144,7 +144,6 @@ describe('--embed --listen UI', function()
     helpers.skip(helpers.is_os('win'))
     clear()
     local child_server = assert(helpers.new_pipename())
-    uv.fs_unlink(child_server)
     funcs.jobstart({nvim_prog, '--embed', '--listen', child_server, '--clean'})
     retry(nil, nil, function() neq(nil, uv.fs_stat(child_server)) end)