Fix clippy from the future (#687)

- `get_first`

Author: sholderbach

src/hinter/cwd_aware.rs

@@ -53,7 +53,7 @@ impl Hinter for CwdAwareHinter {
                         history.session(),
                     ))
                     .unwrap_or_default()
-                    .get(0)
+                    .first()
                     .map_or_else(String::new, |entry| {
                         entry
                             .command_line

src/hinter/default.rs

@@ -23,7 +23,7 @@ impl Hinter for DefaultHinter {
                     history.session(),
                 ))
                 .expect("todo: error handling")
-                .get(0)
+                .first()
                 .map_or_else(String::new, |entry| {
                     entry
                         .command_line