[breaking change] Update edition from 2018 to 2021

And fix clippy warnings

src/blob/mod.rs

@@ -274,7 +274,6 @@ impl Blob<'_> {
     #[inline]
     #[must_use]
     pub fn len(&self) -> usize {
-        use std::convert::TryInto;
         self.size().try_into().unwrap()
     }