richedit: Removed ME_InsertRun since it uses character offsets.

The function was used in one place, and was simply a wrapper around a
call to ME_InsertRunAtCursor, so I removed it to avoids it use in other
parts of the code.
diff --git a/dlls/riched20/undo.c b/dlls/riched20/undo.c
index 908a5ac..e3ebbfb 100644
--- a/dlls/riched20/undo.c
+++ b/dlls/riched20/undo.c
@@ -307,7 +307,12 @@
   }
   case diUndoInsertRun:
   {
-    ME_InsertRun(editor, pItem->member.run.nCharOfs, pItem);
+    ME_Cursor tmp;
+    ME_CursorFromCharOfs(editor, pItem->member.run.nCharOfs, &tmp);
+    ME_InsertRunAtCursor(editor, &tmp, pItem->member.run.style,
+                         pItem->member.run.strText->szData,
+                         pItem->member.run.strText->nLen,
+                         pItem->member.run.nFlags);
     break;
   }
   case diUndoDeleteRun: