fix changelog: remove duplicate entry and fix spelling

changelog.md

@@ -19,7 +19,7 @@ when upgrading from a version of rust-sdl2 to another.
 
 [PR #1250](https://github.com/Rust-SDL2/rust-sdl2/pull/1250) Add `lib64` to native library search path when using bundled feature
 
-[PR #1240](https://github.com/Rust-SDL2/rust-sdl2/pull/1240) **BREAKING CHANGE** Take `PixelMasks` by refrence
+[PR #1240](https://github.com/Rust-SDL2/rust-sdl2/pull/1240) **BREAKING CHANGE** Take `PixelMasks` by reference
 
 [PR #1254](https://github.com/Rust-SDL2/rust-sdl2/pull/1254) **BREAKING CHANGE** Make `SdlDrop` and `SubsystemDrop` safer; forbid external code from constructing `SdlDrop`
 
@@ -31,8 +31,6 @@ when upgrading from a version of rust-sdl2 to another.
 
 [PR #1337](https://github.com/Rust-SDL2/rust-sdl2/pull/1337) Fix "Cannot initialize Sdl from more than one thread" for tests / CI
 
-[PR #1337](https://github.com/Rust-SDL2/rust-sdl2/pull/1337) Fix "Cannot initialize Sdl from more than one thread" for tests / CI
-
 [PR #1346](https://github.com/Rust-SDL2/rust-sdl2/pull/1346) Add basic Shaped Window support
 
 [PR #1314](https://github.com/Rust-SDL2/rust-sdl2/pull/1314) Add "ALWAYS ON TOP" support for X11