test/py: Shorten u_boot_console

This fixture name is quite long and results in lots of verbose code.
We know this is U-Boot so the 'u_boot_' part is not necessary.

But it is also a bit of a misnomer, since it provides access to all the
information available to tests. It is not just the console.

It would be too confusing to use con as it would be confused with
config and it is probably too short.

So shorten it to 'ubman'.

Signed-off-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/u-boot/CAFLszTgPa4aT_J9h9pqeTtLCVn4x2JvLWRcWRD8NaN3uoSAtyA@mail.gmail.com/
diff --git a/doc/develop/tests_writing.rst b/doc/develop/tests_writing.rst
index 5f3c43d..d5917fe 100644
--- a/doc/develop/tests_writing.rst
+++ b/doc/develop/tests_writing.rst
@@ -116,19 +116,19 @@
 in Python::
 
    @pytest.mark.buildconfigspec('cmd_memory')
-   def test_md(u_boot_console):
+   def test_md(ubman):
        """Test that md reads memory as expected, and that memory can be modified
        using the mw command."""
 
-       ram_base = u_boot_utils.find_ram_base(u_boot_console)
+       ram_base = u_boot_utils.find_ram_base(ubman)
        addr = '%08x' % ram_base
        val = 'a5f09876'
        expected_response = addr + ': ' + val
-       u_boot_console.run_command('mw ' + addr + ' 0 10')
-       response = u_boot_console.run_command('md ' + addr + ' 10')
+       ubman.run_command('mw ' + addr + ' 0 10')
+       response = ubman.run_command('md ' + addr + ' 10')
        assert(not (expected_response in response))
-       u_boot_console.run_command('mw ' + addr + ' ' + val)
-       response = u_boot_console.run_command('md ' + addr + ' 10')
+       ubman.run_command('mw ' + addr + ' ' + val)
+       response = ubman.run_command('md ' + addr + ' 10')
        assert(expected_response in response)
 
 This runs a few commands and checks the output. Note that it runs a command,