remove unused flag from horizontal sizer

[seanbudd]

Link to issue number:

closes #12151

Summary of the issue:

The settings dialog NVDA Menu/Preferences/Input Gestures does not open. This is because an alignment flag that was previously ignored now throws an error in the latest wxWidgets.

Traceback:

ERROR - unhandled exception (22:33:34.752) - MainThread (8792):
Traceback (most recent call last):
  File "gui\__init__.pyc", line 301, in onInputGesturesCommand
  File "gui\__init__.pyc", line 193, in _popupSettingsDialog
  File "gui\inputGestures.pyc", line 575, in __init__
  File "gui\settingsDialogs.pyc", line 158, in __init__
  File "gui\inputGestures.pyc", line 611, in makeSettings
wx._core.wxAssertionError: C++ assertion "!(flags & wxALIGN_RIGHT)" failed at ..\..\src\common\sizer.cpp(2168) in wxBoxSizer::DoInsert(): Horizontal alignment flags are ignored in horizontal sizers
NVDA version alpha-21895,52bf1ed6

Description of how this pull request fixes the issue:

Removes the alignment flag.

Testing strategy:

Open the Input Gestures settings dialog and ensure the layout and functionality is the same.

Ensure that the flags wx.ALIGN_LEFT, wx.ALIGH_RIGHT, wx.ALIGN_CENTER_HORIZONTAL, are only used in wx.VERTICAL oriented sizers

Ensure that the flag wx.ALIGN_CENTER_VERTICAL is only used in wx.HORIZONTAL oriented sizers

Known issues with pull request:

None

Change log entry:

None (fixes regression with unreleased python3.8/wxWidgets alpha upgrade)

Code Review Checklist:

• Pull Request description is up to date.
• Unit tests.
• System (end to end) tests.
• Manual tests.
• User Documentation.
• Change log entry.
• Context sensitive help for GUI changes.

[AppVeyorBot]

• System test failure
• Build (for testing PR)

See test results for failed build of commit a8fa24f386