Remove unused string for key label

Bug: 3230041
Change-Id: I1c3cc78157f30f43a5b4a32e413fb43df1db4907
diff --git a/java/res/values/strings.xml b/java/res/values/strings.xml
index 09449dc..5daa989 100644
--- a/java/res/values/strings.xml
+++ b/java/res/values/strings.xml
@@ -226,12 +226,6 @@
     <string name="label_to_alpha_key">ABC</string>
     <!-- Label for ALT modifier key.  Must be short to fit on key! -->
     <string name="label_alt_key">ALT</string>
-    <!-- Label for Backspace modifier key.  Must be short to fit on key! -->
-    <string name="label_backspace_key">Backspace</string>
-    <!-- Label for Shift modifier key.  Must be short to fit on key! -->
-    <string name="label_shift_key">Shift</string>
-    <!-- Label for Return key.  Must be short to fit on key! -->
-    <string name="label_return_key">Return</string>
     <!-- Label for Shift modifier key of symbol keyboard.  Must be short to fit on key! -->
     <string name="label_more_key">More</string>
     <!-- Label for "Tab" key.  Must be short to fit on key! [CHAR LIMIT=4]-->