Use `file_set::FileSet` and `FileSet` consistently in doc
The first occurrence of `FileSet` has the full path (`file_set::FileSet`),
while every other is simply `FileSet`.
//! free-form via list of globs, it's up to the [`Handle`] to interpret the globs
//! in any specific way.
//!
-//! VFS stores a flat list of files. [`FileSet`] can partition this list of files
-//! into disjoint sets of files. Traversal-like operations (including getting
-//! the neighbor file by the relative path) are handled by the [`FileSet`].
+//! VFS stores a flat list of files. [`file_set::FileSet`] can partition this list
+//! of files into disjoint sets of files. Traversal-like operations (including
+//! getting the neighbor file by the relative path) are handled by the [`FileSet`].
//! [`FileSet`]s are also pushed to salsa and cause it to re-check `mod foo;`
//! declarations when files are created or deleted.
//!
-//! [`file_set::FileSet`] and [`loader::Entry`] play similar, but different roles.
+//! [`FileSet`] and [`loader::Entry`] play similar, but different roles.
//! Both specify the "set of paths/files", one is geared towards file watching,
-//! the other towards salsa changes. In particular, single [`file_set::FileSet`]
+//! the other towards salsa changes. In particular, single [`FileSet`]
//! may correspond to several [`loader::Entry`]. For example, a crate from
//! crates.io which uses code generation would have two [`Entries`] -- for sources
//! in `~/.cargo`, and for generated code in `./target/debug/build`. It will
