Exclude vk_enter from adding to keyboard_string on Enter Press

[amr-salahuddin]

Issue:
The current implementation appends vk_enter to keyboard_string on Enter key press, leading to unexpected behavior.

Changes Made:
Modified the code to exclude vk_enter from being appended to keyboard_string when the Enter key is pressed.
in enigma-dev/ENIGMAsystem/SHELL/Platforms/xlib/XLIBmain.cpp line:71

if (actualKey == enigma_user::vk_backspace) {
    if (!enigma_user::keyboard_string.empty()) enigma_user::keyboard_string.pop_back();
} else if (actualKey != enigma_user::vk_enter) {
    enigma_user::keyboard_string += enigma_user::keyboard_lastchar;
}

Related Issue:
#2080

Please review the changes and confirm that excluding vk_enter addresses the problem.

Thank you for your review!