UI Automation in Windows Console: remove workaround at POSITION_LAST for 21H1

[codeofdusk]

Link to issue number:

microsoft/terminal#7771

Summary of the issue:

From winConsoleUIA.py:

# We must pull back the end by one character otherwise when we collapse to end,
# a console bug results in a textRange covering the entire console buffer!
# Strangely the *very* last character is a special blank point
# so we never seem to miss a real character.

This bug was fixed in microsoft/terminal#7792.

Description of how this pull request fixes the issue:

Removes the workaround for 21H1, restoring correct behaviour in the 21H1 console. The pre-21H1 console is unaffected.

Testing performed:

Tested in 21H1 console.

Known issues with pull request:

Visible range bounding is non-functional until microsoft/terminal#7803 is fixed (PR in pipeline, CC @carlos-zamora). Marking as a draft until a PR fixing visible range bounding has been merged.

Change log entry:

None needed.

[codeofdusk]

Closing in favour of #11722.