[orca] Remove unused variable

[Joanmarie Diggs <joanied src gnome org>]

commit d39e8aac7bf9dc8bc958f4878dff23d1a60878e8
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Tue Nov 21 14:05:49 2017 -0500

    Remove unused variable

 src/orca/where_am_I.py |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)
---
diff --git a/src/orca/where_am_I.py b/src/orca/where_am_I.py
index ecef0f7..c0f2b3a 100644
--- a/src/orca/where_am_I.py
+++ b/src/orca/where_am_I.py
@@ -39,7 +39,6 @@ class WhereAmI:
         about the current object of interest.
         """
         self._script = script
-        self._lastAttributeString = ""
 
     def _adjustObject(self, obj):
         """We want to treat text objects inside list items and table cells as