Line.AnnotationText issue on clearing annotation

[bobbygatedev]

In Line .cs line 285 (clearing annotation)
scintilla.DirectMessage(NativeMethods.SCI_ANNOTATIONGETTEXT, new IntPtr(Index), IntPtr.Zero);
should be
scintilla.DirectMessage(NativeMethods.SCI_ANNOTATIONSETTEXT, new IntPtr(Index), IntPtr.Zero);
as stated in https://scintilla.sourceforge.io/ScintillaDoc.html#SCI_ANNOTATIONSETSTYLES
"To clear annotations call SCI_ANNOTATIONSETTEXT with a NULL pointer."

[xv]

Pull request #484