chore(xtask): Remove unnecessary lifetime

`const` variables are always `'static`. Detected by clippy.

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

xtask/src/release.rs

@@ -127,7 +127,7 @@ fn publish(execute: bool) -> Result<()> {
 }
 
 fn weekly_report() -> Result<()> {
-    const JSON_FIELDS: &'static str = "title,number,url,author";
+    const JSON_FIELDS: &str = "title,number,url,author";
 
     let sh = sh();