Depend on anyhow directly

This removes the proxy via crate::error to depend on anyhow directly.
There is no benefit to this indirection and this makes it simpler to
see which error types are used.

src/imap/scan_folders.rs

@@ -1,9 +1,9 @@
 use std::time::Instant;
 
-use crate::{config::Config, context::Context};
-use anyhow::Context as _;
+use anyhow::{Context as _, Result};
 
-use crate::error::Result;
+use crate::config::Config;
+use crate::context::Context;
 use crate::imap::Imap;
 use async_std::prelude::*;