Fix mismatch of MSRV and prefix lint.

Cargo.toml

@@ -7,7 +7,7 @@ license = "MIT OR Apache-2.0"
 description = "Implementation of the PMTiles v3 spec with multiple sync and async backends."
 repository = "https://github.com/stadiamaps/pmtiles-rs"
 keywords = ["pmtiles", "gis", "geo"]
-rust-version = "1.78.0"
+rust-version = "1.81.0"
 categories = ["science::geo"]
 
 [features]

src/directory.rs

@@ -41,7 +41,7 @@ impl Directory {
     /// Get an estimated byte size of the directory object. Use this for cache eviction.
     #[must_use]
     pub fn get_approx_byte_size(&self) -> usize {
-        self.entries.capacity() * std::mem::size_of::<DirEntry>()
+        self.entries.capacity() * size_of::<DirEntry>()
     }
 }