docs(powershell): use tee.exe instead of Tee-Object

Problem: Tee-Object does not create a file if it does not receive input
for example when :grep does not find matches.
and so nvim tries to open a nonexistent errorfile causing an error.

Solution: use tee.exe instead of Tee-Object

test/functional/ex_cmds/make_spec.lua

@@ -24,10 +24,8 @@ describe(':make', function()
     it('captures stderr & non zero exit code #14349', function ()
       nvim('set_option', 'makeprg', testprg('shell-test')..' foo')
       local out = eval('execute("make")')
-      -- Make program exit code correctly captured
-      matches('\nshell returned 3', out)
       -- Error message is captured in the file and printed in the footer
-      matches('\n.*%: Unknown first argument%: foo', out)
+      matches('[\r\n]+.*[\r\n]+Unknown first argument%: foo[\r\n]+%(1 of 1%)%: Unknown first argument%: foo', out)
     end)
 
     it('captures stderr & zero exit code #14349', function ()