[Cargo.toml] Update repository URL

Cargo.toml

diff --git a/Cargo.toml b/Cargo.toml
index 1dd61ac..16326e8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,7 +15,7 @@
 license-file = "LICENSE"
 keywords = ["boringssl"]
 categories = ["cryptography"]
-repository = "https://github.com/google/mundane"
+repository = "https://mundane.googlesource.com/mundane"
 
 [features]
 insecure = []