fix(rustfmt): avoid unstable inner attributes

See: https://github.com/rust-lang/rust/issues/64266
Signed-off-by: Christina Sørensen <christina@cafkafk.com>

rustfmt.toml

@@ -0,0 +1 @@
+ignore = ['src/options/flags.rs']

src/options/flags.rs

@@ -1,4 +1,3 @@
-#![rustfmt::skip]
 use crate::options::parser::{Arg, Args, TakesValue, Values};
 
 // exa options