remove unused #include to fix musl libc build (facebook#5583)

Summary:
The `#include "core_local.h"` was pulling in libgcc's `posix_memalign()`
declaration. That declaration specifies `throw()` whereas musl libc's
declaration does not. This was leading to the following compiler error
when using musl libc:

```
In file included from /go/src/github.com/cockroachdb/cockroach/c-deps/rocksdb/port/jemalloc_helper.h:26:0,
                 from /go/src/github.com/cockroachdb/cockroach/c-deps/rocksdb/util/jemalloc_nodump_allocator.h:11,
                 from /go/src/github.com/cockroachdb/cockroach/c-deps/rocksdb/util/jemalloc_nodump_allocator.cc:6:
/go/native/x86_64-unknown-linux-musl/jemalloc/include/jemalloc/jemalloc.h:63:29: error: declaration of 'int posix_memalign(void**, size_t, size_t) throw ()' has a different exception specifier
 #  define je_posix_memalign posix_memalign
                             ^
/go/native/x86_64-unknown-linux-musl/jemalloc/include/jemalloc/jemalloc.h:63:29: note: from previous declaration 'int posix_memalign(void**, size_t, size_t)'
 #  define je_posix_memalign posix_memalign
                             ^
/go/native/x86_64-unknown-linux-musl/jemalloc/include/jemalloc/jemalloc.h:202:38: note: in expansion of macro 'je_posix_memalign'
 JEMALLOC_EXPORT int JEMALLOC_NOTHROW je_posix_memalign(void **memptr,
                                      ^~~~~~~~~~~~~~~~~
make[4]: *** [CMakeFiles/rocksdb.dir/util/jemalloc_nodump_allocator.cc.o] Error 1
```

Since `#include "core_local.h"` is not actually used, we can just remove
it. I verified that fixes the build.

There was a related PR here (facebook#2188), although the problem description is
slightly different.
Pull Request resolved: facebook#5583

Differential Revision: D16343227

fbshipit-source-id: 0386bc2b5fd55b2c3b5fba19382014efa52e44f8

memory/jemalloc_nodump_allocator.h

@@ -11,7 +11,6 @@
 #include "port/jemalloc_helper.h"
 #include "port/port.h"
 #include "rocksdb/memory_allocator.h"
-#include "util/core_local.h"
 #include "util/thread_local.h"
 
 #if defined(ROCKSDB_JEMALLOC) && defined(ROCKSDB_PLATFORM_POSIX)