[lldb] Avoid flickering by not clearing the statusline when redrawing

When redrawing the statusline, the current implementation would clear
the current line before drawing the new content. Since we always
overwrite the whole statusline from beginning to end, there's no need to
clear it and we can avoid the potential for flickering.

(cherry picked from commit 55b9515)

Author: JDevlieghere

lldb/source/Core/Statusline.cpp

@@ -75,7 +75,6 @@ void Statusline::Draw(std::string str) {
   locked_stream << ANSI_SAVE_CURSOR;
   locked_stream.Printf(ANSI_TO_START_OF_ROW,
                        static_cast<unsigned>(m_terminal_height));
-  locked_stream << ANSI_CLEAR_LINE;
   locked_stream << str;
   locked_stream << ANSI_NORMAL;
   locked_stream << ANSI_RESTORE_CURSOR;