Normalized instances of `N.B.`.

src/query.md

@@ -190,7 +190,7 @@ pub fn provide(providers: &mut Providers) {
 fn fubar<'cx, 'tcx>(tcx: TyCtxt<'cx, 'tcx>, key: DefId) -> Fubar<'tcx> { .. }
 ```
 
-NB. Most of the `rustc_*` crates only provide **local
+N.B. Most of the `rustc_*` crates only provide **local
 providers**. Almost all **extern providers** wind up going through the
 [`rustc_metadata` crate][rustc_metadata], which loads the information from the crate
 metadata.  But in some cases there are crates that provide queries for

src/ty.md

@@ -102,7 +102,7 @@ The `sty` field (the origin of this name is unclear to me; perhaps
 structural type?) is of type `TypeVariants<'tcx>`, which is an enum
 defining all of the different kinds of types in the compiler.
 
-> NB: inspecting the `sty` field on types during type inference can be
+> N.B. inspecting the `sty` field on types during type inference can be
 > risky, as there may be inference variables and other things to
 > consider, or sometimes types are not yet known that will become
 > known later.).