apply clippy advices on executor/commands lifetimes.

src/benchmark/executor.rs

@@ -110,7 +110,7 @@ impl<'a> RawExecutor<'a> {
     }
 }
 
-impl<'a> Executor for RawExecutor<'a> {
+impl Executor for RawExecutor<'_> {
     fn run_command_and_measure(
         &self,
         command: &Command<'_>,
@@ -161,7 +161,7 @@ impl<'a> ShellExecutor<'a> {
     }
 }
 
-impl<'a> Executor for ShellExecutor<'a> {
+impl Executor for ShellExecutor<'_> {
     fn run_command_and_measure(
         &self,
         command: &Command<'_>,

src/command.rs

@@ -383,7 +383,7 @@ fn test_get_parameterized_command_name() {
     assert_eq!(cmd.get_name(), "name-quux-baz");
 }
 
-impl<'a> fmt::Display for Command<'a> {
+impl fmt::Display for Command<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", self.get_command_line())
     }