fix: Typo in architecture.md

Author: alexfertel

docs/dev/architecture.md

@@ -212,7 +212,7 @@ If you want to use IDE parts of rust-analyzer via LSP, custom flatbuffers-based
 The API uses editor's terminology, it talks about offsets and string labels rather than in terms of definitions or types.
 It is effectively the view in MVC and viewmodel in [MVVM](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93viewmodel).
 All arguments and return types are conceptually serializable.
-In particular, syntax tress and hir types are generally absent from the API (but are used heavily in the implementation).
+In particular, syntax trees and hir types are generally absent from the API (but are used heavily in the implementation).
 Shout outs to LSP developers for popularizing the idea that "UI" is a good place to draw a boundary at.
 
 `ide` is also the first crate which has the notion of change over time.