Correct a stale reference to GIT_EBAREINDEX
diff --git a/include/git2/index.h b/include/git2/index.h
index ae919e1..dad4234 100644
--- a/include/git2/index.h
+++ b/include/git2/index.h
@@ -159,7 +159,7 @@ typedef enum {
*
* Since there is no ODB or working directory behind this index,
* any Index methods which rely on these (e.g. index_add) will
- * fail with the GIT_EBAREINDEX error code.
+ * fail with the GIT_ERROR error code.
*
* If you need to access the index of an actual repository,
* use the `git_repository_index` wrapper.