[librsvg] Update Cargo.lock; this just adds an auto-generated comment

[Federico Mena Quintero <federico src gnome org>]

commit 32045132293d080bd473e2fa580950655c192aab
Author: Federico Mena Quintero <federico gnome org>
Date:   Thu Feb 7 16:25:55 2019 -0600

    Update Cargo.lock; this just adds an auto-generated comment

 Cargo.lock | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/Cargo.lock b/Cargo.lock
index 734d79d9..a76d8b47 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,3 +1,5 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
 [[package]]
 name = "aho-corasick"
 version = "0.6.9"