remove duplicate section of user-changes.md (#1477)

"Enable shared dependencies by default" was in there twice.

doc/user-changes.md

@@ -49,37 +49,6 @@ automatic updates.
 When enabled, updates may happen before executing commands that rely on
 indexes: `get`, `search`, `with`, etc.
 
-### Enable shared dependencies by default
-
-PR [#1449](https://github.com/alire-project/alire/pull/1449)
-
-Pre-2.0, Alire worked always in "sandboxed" mode; that is, all source
-dependencies were found under `<workspace>/alire/cache`. This behavior can be
-now enabled with `alr config --set dependencies.shared false`, locally or
-globally.
-
-By default, post-2.0, Alire works in "shared" mode, where sources are
-downloaded once (to `~/.cache/alire/releases`) and unique builds are created
-(under `~/.cache/alire/builds`) for unique configurations. This should minimize
-rebuilds across crate configurations and workspaces, and eliminate risks of
-inconsistencies.
-
-Disk use is decreased by unique source downloads, but might be increased by
-unique build configurations. Cache management and cleanup will be provided down
-the road. The build cache can always be deleted to retrieve disk space, at the
-cost of triggering rebuilds.
-
-Unique builds are identified by a build hash which takes into account the
-following inputs for a given release:
-
-- Build profile
-- Environment variables modified in the manifest
-- GPR external variables declared or set
-- Configuration variables declared or set
-- Compiler version
-- Vaue of `LIBRARY_TYPE` and `<CRATE>_LIBRARY_TYPE` variables.
-- Hash of dependencies
-
 ### Deprecation of `dependencies.dir` in favor of `dependencies.shared`
 
 PR [#1419](https://github.com/alire-project/alire/pull/1419)