Use US English spelling of "behavior" and "customize" (#15117)

This PR fixes some instances that weren't using US English spellings of
"behavior" and "customize".

Release Notes:

- N/A

crates/editor/src/editor.rs

@@ -11,7 +11,7 @@
 //!
 //! All other submodules and structs are mostly concerned with holding editor data about the way it displays current buffer region(s).
 //!
-//! If you're looking to improve Vim mode, you should check out Vim crate that wraps Editor and overrides its behaviour.
+//! If you're looking to improve Vim mode, you should check out Vim crate that wraps Editor and overrides its behavior.
 pub mod actions;
 mod blame_entry_tooltip;
 mod blink_manager;