Fix clippy lints (#861)

* Remove dead docstring

The respective function has been removed a while ago.

* Elide unused named lifetimes

src/completion/history.rs

@@ -13,7 +13,7 @@ pub(crate) struct HistoryCompleter<'menu>(&'menu dyn History);
 
 // Safe to implement Send since the HistoryCompleter should only be used when
 // updating the menu and that must happen in the same thread
-unsafe impl<'menu> Send for HistoryCompleter<'menu> {}
+unsafe impl Send for HistoryCompleter<'_> {}
 
 fn search_unique(
     completer: &HistoryCompleter,
@@ -30,7 +30,7 @@ fn search_unique(
         .filter(move |value| seen_matching_command_lines.insert(value.command_line.clone())))
 }
 
-impl<'menu> Completer for HistoryCompleter<'menu> {
+impl Completer for HistoryCompleter<'_> {
     fn complete(&mut self, line: &str, pos: usize) -> Vec<Suggestion> {
         match search_unique(self, line) {
             Err(_) => vec![],

src/history/base.rs

@@ -183,8 +183,6 @@ pub trait History: Send {
     /// load a history item by its id
     fn load(&self, id: HistoryItemId) -> Result<HistoryItem>;
 
-    /// retrieves the next unused session id
-
     /// count the results of a query
     fn count(&self, query: SearchQuery) -> Result<i64>;
     /// return the total number of history items