Update release notes

(cherry picked from commit 32166ab)

Author: Mark-Simulacrum

RELEASES.md

@@ -1,10 +1,12 @@
 Version 1.45.1 (2020-07-30)
 ==========================
 
+* [Fix const propagation with references.][73613]
 * [rustfmt accepts rustfmt_skip in cfg_attr again.][73078]
 * [Avoid spurious implicit region bound.][74509]
 * [Install clippy on x.py install][74457]
 
+[73613]: https://github.com/rust-lang/rust/pull/73613
 [73078]: https://github.com/rust-lang/rust/issues/73078
 [74509]: https://github.com/rust-lang/rust/pull/74509
 [74457]: https://github.com/rust-lang/rust/pull/74457