Remove unused crc64 function

Signed-off-by: Paul Jones <paul@pauljones.id.au>

include/crucible/crc64.h

@@ -8,7 +8,6 @@
 namespace crucible {
 	namespace Digest {
 		namespace CRC {
-			uint64_t crc64(const char *s);
 			uint64_t crc64(const void *p, size_t len);
 		};
 	};