Add blank lines after module-level // comments.

Similar to the previous commit.

Author: nnethercote

Diff for: core/tests/net/parser.rs

@@ -1,4 +1,5 @@
 // FIXME: These tests are all excellent candidates for AFL fuzz testing
+
 use core::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
 use core::str::FromStr;
 

Diff for: core/tests/pin_macro.rs

@@ -1,4 +1,5 @@
 // edition:2021
+
 use core::{
     marker::PhantomPinned,
     mem::{drop as stuff, transmute},