Use implicit copy-constructor generated by compiler

This also suppresses the following clang warning:
warning: definition of implicit copy assignment operator for 'Version<unsigned short, 2>' is deprecated because it has a user-declared copy constructor [-Wdeprecated-copy]

src/base/digest32.h

@@ -41,7 +41,6 @@ public:
     using UnderlyingType = lt::digest32<N>;
 
     Digest32() = default;
-    Digest32(const Digest32 &other) = default;
 
     Digest32(const UnderlyingType &nativeDigest)
         : m_valid {true}