[libcxx][test] Use bool allocators for vector<bool>::get_allocator test

[CaseyCarter]

Summary

... to be consistent with other get_allocator tests, and to avoid requiring vector<T, allocator<U>> to be valid.

[• Quuxplusone]

LGTM if CI is green!

[Mordante]

LGTM!

[philnik]

@CaseyCarter Is there a reason you aren't landing this? You have commit access, right?

[CaseyCarter]

I landed this months ago, but failed to autolink the Differential to the commit. This is officially closed by 93230ac1d2cf32419ce88fdd850f92a02bec5553.

libcxx/test/std/containers/sequences/vector.bool/get_allocator.pass.cpp

 #include <vector>
 #include <cassert>
 
 #include "test_allocator.h"
 #include "test_macros.h"
 
 int main(int, char**) {
     {
-        std::allocator<int> alloc;
+        std::allocator<bool> alloc;
         const std::vector<bool> vb(alloc);
         assert(vb.get_allocator() == alloc);
     }
     {
-        other_allocator<int> alloc(1);
-        const std::vector<bool, other_allocator<int> > vb(alloc);
+        other_allocator<bool> alloc(1);
+        const std::vector<bool, other_allocator<bool> > vb(alloc);
         assert(vb.get_allocator() == alloc);
     }
 
     return 0;
 }