Ignore single_match_else pedantic clippy lint in test

    warning: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
      --> tests/test_lit.rs:16:5
       |
    16 | /     match TokenStream::from_str(s)
    17 | |         .unwrap()
    18 | |         .into_iter()
    19 | |         .next()
    ...  |
    23 | |         _ => panic!(),
    24 | |     }
       | |_____^
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#single_match_else
       = note: `-W clippy::single-match-else` implied by `-W clippy::pedantic`
       = help: to override `-W clippy::pedantic` add `#[allow(clippy::single_match_else)]`
    help: try
       |
    16 ~     if let TokenTree::Literal(lit) = TokenStream::from_str(s)
    17 +         .unwrap()
    18 +         .into_iter()
    19 +         .next()
    20 +         .unwrap() { Lit::new(lit) } else { panic!() }
       |

tests/test_lit.rs

@@ -1,6 +1,7 @@
 #![allow(
     clippy::float_cmp,
     clippy::non_ascii_literal,
+    clippy::single_match_else,
     clippy::uninlined_format_args
 )]