morphisms: remove 'return 0;' at end since it is now added by default

morphisms/length_prefix.morphism-base

@@ -10,8 +10,6 @@ morph_array_as_valterm_to_lenpfx (Terminator:native.UInt8)
     length_prefix_uint64_t_array_uint8_t_clear(dst);
     while( *src != Terminator )
         length_prefix_uint64_t_array_uint8_t_push(dst, *src++);
-
-    return 0;
 ```
 
 
@@ -23,8 +21,6 @@ morph_array_as_lenpfx_to_valterm (Terminator:native.UInt8)
         *dst++ = src->items[i];
 
     *dst = Terminator;
-
-    return 0;
 ```
 
 morph_array_as_lenpfx_to_continuation_bit (T:Type)
@@ -42,6 +38,4 @@ morph_array_as_lenpfx_to_continuation_bit (T:Type)
         if( i+1 < src->len )
             dst[i] |= (1<<(n_bits-1));
     }
-
-    return 0;
 ```