audit.toml: Add Marvin Attack from rsa crate to ignore list

The rsa crate is only used for testing purpose and the security
vulnerability has no impact on this crate.

Signed-off-by: Gowtham Suresh Kumar <[email protected]>

Author: gowthamsk-arm

.cargo/audit.toml

@@ -0,0 +1,4 @@
+[advisories]
+ignore = [
+    "RUSTSEC-2023-0071", # `rsa` Marvin Attack not concerning as `rsa` is only used for tests
+]