wxGUI: remove unnecessary key press event handlers

[tmszi]

Describe the bug
With pressing any key is printed error message.

To Reproduce
Steps to reproduce the behavior:

1. Launch Win GRASS GIS wxGUI (single or multi window mode)
2. Click on the main toolbar panel widget to get a focus
3. Press any key e.g. Shift
4. See error

Single window mode error:

Traceback (most recent call last):
  File "C:\Program Files\GRASS GIS
8.3\gui\wxpython\lmgr\frame.py", line 2243, in OnKeyDown

if event.CtrlDown():
AttributeError
:
'KeyEvent' object has no attribute 'CtrlDown'

Multi window mode error:

Traceback (most recent call last):
  File "C:\Program Files\GRASS GIS
8.3\gui\wxpython\main_window\frame.py", line 2284, in
OnKeyDown

if event.CtrlDown():
AttributeError
:
'KeyEvent' object has no attribute 'CtrlDown'

Expected behavior
With pressing any key should not be printed any error message.

System description:

• Operating System: MS Windows
• GRASS GIS version: all

Additional context
Keyboard shortcut for add raster map is Ctrl + Shift +R and for vector map is Ctrl + Shift + V defined here:

grass/gui/wxpython/xml/wxgui_items.xml

Lines 157 to 168 in 59e2974

	<wxgui-item name="AddRaster">
	<label>Add raster</label>
	<handler>OnAddRaster</handler>
	<description>Add raster map layer to current display</description>
	<shortcut>Ctrl+Shift+R</shortcut>
	</wxgui-item>
	<wxgui-item name="AddVector">
	<label>Add vector</label>
	<handler>OnAddVector</handler>
	<description>Add vector map layer to current display</description>
	<shortcut>Ctrl+Shift+V</shortcut>
	</wxgui-item>

[petrasovaa]

Thanks!