Remove outdated web hot reload comment from architectural overview (#12657)

Small change to architectural-overview.md to remove a stale comment (as
of Flutter 3.35, the current stable release) about stateful hot reload
not being enabled by default.

Author: elitree

src/content/resources/architectural-overview.md

@@ -26,17 +26,13 @@ much code as possible.
 
 During development, Flutter apps run in a VM that offers
 stateful hot reload of changes without needing a full recompile.
-(On web, Flutter supports hot restart and
-[hot reload behind a flag][].)
 For release, Flutter apps are compiled directly to machine code,
 whether Intel x64 or ARM instructions,
 or to JavaScript if targeting the web.
 The framework is open source, with a permissive BSD license,
 and has a thriving ecosystem of third-party packages that
 supplement the core library functionality.
 
-[hot reload behind a flag]: /platform-integration/web/building#hot-reload-web
-
 This overview is divided into a number of sections:
 
 1. The **layer model**: The pieces from which Flutter is constructed.