RUSTSEC-2020-0011: mark as informational

See discussion on #275 (comment)

Author: tarcieri

crates/plutonium/RUSTSEC-2020-0011.toml

@@ -2,6 +2,7 @@
 id = "RUSTSEC-2020-0011"
 package = "plutonium"
 date = "2020-04-23"
+informational = "notice"
 title = "Crate intended to hide unsafe use."
 url = "https://www.reddit.com/r/rust/comments/g5rsuh/show_me_the_most_illegal_rust_code_youve_ever/fo88z2d?utm_source=share&utm_medium=web2x"
 description = """