rust/pv: Fix 'elided_lifetimes_in_associated_constant' warning

Fixes "warning: `&` without an explicit lifetime name cannot be used
here". This warning will become a hard error in "the future". For more
information, see issue #115010 <rust-lang/rust#115010>

Closes: #162
Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

rust/pv/src/error.rs

@@ -46,8 +46,8 @@ pub enum Error {
 // used in macros
 #[doc(hidden)]
 impl Error {
-    pub const CRL: &str = "CRL";
-    pub const CERT: &str = "certificate";
+    pub const CRL: &'static str = "CRL";
+    pub const CERT: &'static str = "certificate";
 }
 
 /// Error cases for verifying host-key documents