Update changelog for #264

Author: phil-opp

Changelog.md

@@ -2,6 +2,7 @@
 
 # 0.14.5 – 2021-09-04
 
+- Add `clean_up` and `clean_up_with_filter` methods to deallocate unused page tables ([#264](https://github.com/rust-osdev/x86_64/pull/264))
 - Rename some XCr0 and CR4 flags (#[275](https://github.com/rust-osdev/x86_64/pull/275))
 - Expose `MapperFlush::new` and `MapperFlushAll::new` constructor functions ([#296](https://github.com/rust-osdev/x86_64/pull/296))
 - Use `#[cfg(doc)]` instead of docs.rs-specific cfg flag (#[287](https://github.com/rust-osdev/x86_64/pull/287))