Add blank lines after module-level //! comments.

Most modules have such a blank line, but some don't. Inserting the blank
line makes it clearer that the `//!` comments are describing the entire
module, rather than the `use` declaration(s) that immediately follows.

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs

@@ -1,5 +1,6 @@
 //! Error Reporting for Anonymous Region Lifetime Errors
 //! where one region is named and the other is anonymous.
+
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::{
     errors::ExplicitLifetimeRequired,

compiler/rustc_infer/src/infer/freshen.rs

@@ -30,6 +30,7 @@
 //! solving a set of constraints. In contrast, the type inferencer assigns a value to each type
 //! variable only once, and it does so as soon as it can, so it is reasonable to ask what the type
 //! inferencer knows "so far".
+
 use super::InferCtxt;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::bug;

compiler/rustc_infer/src/infer/outlives/mod.rs

@@ -1,4 +1,5 @@
 //! Various code related to computing outlives relations.
+
 use self::env::OutlivesEnvironment;
 use super::region_constraints::RegionConstraintData;
 use super::{InferCtxt, RegionResolutionError, SubregionOrigin};