Adapt to renaming of MakeReadOnly->MakeReadOnlyObj

[fingolfin]

This adapts ZeroMQInterface to the changes in https://github.com/gap-system/gap/pull/1870

[codecov[bot]]

Codecov Report

Merging #14 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #14   +/-   ##
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  Coverage   35.62%   35.62%           
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  Files           2        2           
  Lines         379      379           
  Branches       67       67           
=======================================
  Hits          135      135           
  Misses        222      222           
  Partials       22       22

[markuspf]

This package requires GAP 4.9 or later, hence the backwards-compatibility code is not really necessary.

[fingolfin]

Updated