Suppress range_plus_one lint

I find this easier to understand in combination with the line right
after.

impl/src/fmt.rs

@@ -18,7 +18,7 @@ impl Display<'_> {
         let mut has_bonus_display = false;
 
         while let Some(brace) = read.find('{') {
-            out += &read[..=brace];
+            out += &read[..brace + 1];
             read = &read[brace + 1..];
             if read.starts_with('{') {
                 out.push('{');

impl/src/lib.rs

@@ -1,4 +1,4 @@
-#![allow(clippy::block_in_if_condition_stmt)]
+#![allow(clippy::block_in_if_condition_stmt, clippy::range_plus_one)]
 
 extern crate proc_macro;