fix usages after rename

crates/ra_ide_api_light/src/lib.rs

@@ -1,3 +1,8 @@
+//! This crate provides thouse IDE features which use only a single file.
+//!
+//! This usually means functions which take sytnax tree as an input and produce
+//! an edit or some auxilarly info.
+
 pub mod assists;
 mod extend_selection;
 mod folding_ranges;