[allocator.requirements.general] Remove redundant template syntax

In the Cpp17Allocator requirements, all identifiers name specific
types, even if they are template instantiations.  Hence, all use
of `typename`, `.template`, and `::template` is redundant.  Not
in the sense of we are awaiting LWG to review P2150 for policy,
but in the sense these have been redundant since C++11, and were
outright ill-formed prior to that.

The majority of the wording throughout this subclause already
(correctly) avoids use of these redundant keywords.  This PR
brings the title rows into agreement with the body text, and
fixes one outstanding redundant use of `::template`.

Author: AlisdairM

source/lib-intro.tex

@@ -2020,7 +2020,7 @@
 defaults for different requirements than the primary template.
 
 \begin{itemdecl}
-typename X::pointer
+X::pointer
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2030,7 +2030,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::const_pointer
+X::const_pointer
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2044,8 +2044,8 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::void_pointer
-typename Y::void_pointer
+X::void_pointer
+Y::void_pointer
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2061,8 +2061,8 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::const_void_pointer
-typename Y::const_void_pointer
+X::const_void_pointer
+Y::const_void_pointer
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2080,7 +2080,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::value_type
+X::value_type
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2090,7 +2090,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::size_type
+X::size_type
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2106,7 +2106,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::difference_type
+X::difference_type
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2122,7 +2122,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::template rebind<U>::other
+X::rebind<U>::other
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2133,7 +2133,7 @@
 \pnum
 \ensures
 For all \tcode{U} (including \tcode{T}),
-\tcode{Y::template rebind<T>::other} is \tcode{X}.
+\tcode{Y::rebind<T>::other} is \tcode{X}.
 
 \pnum
 \remarks
@@ -2578,7 +2578,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::propagate_on_container_copy_assignment
+X::propagate_on_container_copy_assignment
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2600,7 +2600,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::propagate_on_container_move_assignment
+X::propagate_on_container_move_assignment
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2622,7 +2622,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::propagate_on_container_swap
+X::propagate_on_container_swap
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2644,7 +2644,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-typename X::is_always_equal
+X::is_always_equal
 \end{itemdecl}
 
 \begin{itemdescr}