Remove rules from names intro

This whole section was intended as an introduction that just defined
some terms. There is no need to link to these individually, since the
things they introduce have their own chapters.

Author: ehuss

src/names.md

@@ -7,32 +7,25 @@ the source program, usually via a [path]. Entities include [types], [items],
 [generic parameters], [variable bindings], [loop labels], [lifetimes],
 [fields], [attributes], and [lints].
 
-r[names.decl]
 A *declaration* is a syntactical construct that can introduce a *name* to
 refer to an entity. Entity names are valid within a [*scope*] --- a region of
 source text where that name may be referenced.
 
-r[names.explicit-decl]
 Some entities are [explicitly declared](#explicitly-declared-entities) in the
 source code, and some are [implicitly declared](#implicitly-declared-entities)
 as part of the language or compiler extensions.
 
-r[names.path]
 [*Paths*] are used to refer to an entity, possibly in another module or type.
 
-r[names.lifetime]
 Lifetimes and loop labels use a [dedicated syntax][lifetimes-and-loop-labels] using a
 leading quote.
 
-r[names.namespace]
 Names are segregated into different [*namespaces*], allowing entities in
 different namespaces to share the same name without conflict.
 
-r[names.resolution]
 [*Name resolution*] is the compile-time process of tying paths, identifiers,
 and labels to entity declarations.
 
-r[names.visibility]
 Access to certain names may be restricted based on their [*visibility*].
 
 r[names.explicit]