Fix minor build errors

[PizieDust]

Errors:

311 |               a_contenteditable true;
                                      ^^^^
Error: This expression should not be a boolean literal, the expected type is
       Html_types.contenteditable_value

Error: This expression has type value:string ->
                                ([< Html_types.data_attrib ],
                                 [< Html_types.data_content_fun ],
                                 [> Html_types.data ])
                                star
       which is not a record type.
File "unikernel_update.ml", line 512, characters 40-44:

[hannesm]

this is for tyxml 5.0.0 -- could you adjust the bounds in config.ml and mollymawk_libraries.opam?